Update (08 Sep 2019): Some of the stamps on my wish list have been issued recently. I've added some more subjects and details that I hope are considered when finalizing the stamp issues over the next few years.
Update (23 Jun 2019): I've been making minor updates to this list. A few of the stamps on the wish list have been getting approved, so that's a cool thing. I'm hoping India Post takes input from stamp collectors in building out the stamp issue program for the next several years and keeps the average cost for collectors somewhat manageable.
Original Post (04 Oct 2018): This post will be a source to aggregate stamp subject suggestions or ideas that India Post can use to design stamp programs for future years. I have posted some of this information in couple of other posts and on the twitter feed as well. The list is simply organized by year, and separately lists some other personalities, events and themes that I'd like to see being issued as postal stamps. Feel free to leave your ideas in the comments section below. When I make modifications, those will all be mentioned at the bottom of this post.
2018
19th Kushok Bakula Rinpoche
Acharya Bodhidharma
Bhairon Singh Shekhawat (Approved)
Chandrakant T. Patel
Dhanraj Bhagat
L. L. Narayan
Laxmanrao Inamdar
Ramanand Sagar
Sikander Bhakt
Srimant Sankardev
Vinda Karandikar
100 Years of Kheda Movement
100 Years of Sabarmati Ashram
The Maihar Band (100 Years)
The Yoga Institute, Mumbai (100 Years)
Amrita Pritam
Chandrashekhar Saraswati Mahaperiyavar
I. K. Gujral
Kasturba Gandhi (75th Death Anniversary)
Maharani Gayatri Devi
Maniram Dewan
Raja Todarmal
Rana Kumbha (600th Birth Anniversary)
Shivmangal Singh Suman
Sudhir Phadke
Vijaya Raje Scindia (Approved)
50 Years of Rajdhani Express
Auckland House School, Shimla
CMC Ludhiana
High Court of Punjab & Haryana Centenary
ISRO - Golden Jubilee (Magalyaan, Chandrayan and Vikram Sarabhai)
La Martiniere Girls’ College, Lucknow (150 Years)
Margazhi Music Season (Brahma & Thyaga Brahma Gana Sabhas)
Rajkumar College, Rajkot (150 Years)
Pandurang Shastri Athavle
Sheikh Mujibur Rahman
36th International Geological Congress
Modern School, New Delhi
Shiromani Gurdwara Parbandhak Committee
2021
75 Years of India's Independence
India-Bangladesh: Joint Issue (50 & 75 Years of Independence)
Other Events & Organizations
Bishop Cotton School, Bengaluru
Gir Wildlife Sanctuary
Architecture
Art & Culture
Caves - Ajanta, Borra, Ellora, Elephanta, Kanheri, Badami, Bhimbhetka, Kandagiri, Undavalli, Udayagiri
Dams and Reservoirs
Famous Libraries - Allahabad Public, Saraswathi Mahal, Amar Mahal, Asiatic Society Mumbai, Goa, Kerala, Karnataka and Telangana State Central libraries
Festivals - Kullu Dussehra, Holi, Chhath Festival, Janmashtami (Krishna Jayanti), Baisakhi, Raksha Bandhan, Ganesh Utsav, Eid Mubarak
Horses - Spiti and Kati
Indian Lakes - Bhoj Tal, Chilika, Dal Lake, Damdama, Hussain Sagar, Loktak, Naini Tal, Nal Sarovar, Pichola, Pushkar Lake, Sambhar, Suraj Tal, Vembanad, Wular
Indian Perfumes - Musk, Saffron, Khus, Kewra, Vetiver, Champa
Indian Traditions
Joint Stamp Issues with Australia, Bhutan, Germany, Nigeria, Oman, Switzerland, UK, UAE, USA
Jyotirlinga Temples (12 designs)
Landmark Bridges - Dhola Sadiya, Bogibeel
Luxury Trains - Palace on Wheels, Deccan Odyssey, Golden Chariot, Maharajas Express
Master Healers of AYUSH - Rajendra Lal Dutta, P. S. Varier, B. K. S. Iyengar
Medicinal Flowers of AYUSH - Saffron, Rose, Marigold, Violet, Avaram Senna, Hibiscus, Jasmine, Thumba, Neelkamal, Nagchampa, Palash, Sahijana (Drumstick)
Musical Instruments
Natural Heritage - National Parks and Tiger Reserves
Post Office Heritage Buildings - Patna GPO, Bhagalpur HPO, PTC Darbhanga, Mandi HPO, Panaji HPO, Amritsar HPO, Darjeeling HPO, Varanasi HPO, Circle Offices in Bengaluru, Lucknow and Trivandrum
Railway Bridges - Godavari Arch Bridge, Vembanad Bridge, Farakka Barrage, Digha-Sonpur Bridge
Railway Station Buildings
Social Causes - Blood donation, Organ donation, Heart health, Child safety, Prevent child mortality, Epilepsy awareness
Textiles - Chanderi, Maheshwari, Paithani, Jamdani, Kota, Sambalpuri, Angami Weaves, Tat
Toy Trains - Neral Matheran Railway, Nilgiri Mountain Railway
Other Personalities
Ashok Singhal
Babasaheb Apte
Banda Singh Bahadur
B. D. Jatti
Balasaheb Thackarey
Balasheb Deoras
Balraj Madhok
Chinmayananda Saraswati
Dattopant Thengadi (approved)
Dadu Dayal
Dr. Muthulakshmi Reddy
Dayanand Saraswati
Eknath Ranade
Gopal Swarup Pathak
Ghulam Sarwar
J. Jayalalithaa
Kaka Hathrasi
Kesahavdas
K. R. Narayanan
Khushabhau Thakre
Madhukar Rao Bhagwat
Madhvacharya
Makhanlal Chaturvedi
Marnopant Pingley
Mohammad Hidayatullah
M. S. Golwalkar
Nimbakacharya
N. Sanjeeva Reddy
P. V. Narasimha Rao (approved)
Pandurang Kane
Rajendra Singh
Ramchandra Das Paramhans
Raskhan
Sachchidananda Vatsyayan 'Agyeya'
Satguru Ram Singh
Shivmangal Singh Suman
Sita Ram Goel
Siyaram Sharan Gupt
Swami Abhedananda
Swaraj P. Gupta
V. P. Singh
Jnanpith Award Winners
Cartoonists - Sudhir Pillai, Abu Abhraham, Mario Miranda
Musicians/Singers - G. M. Durrani, Mahendra Kapoor, P. B. Sreenivas
Issued by India Post
150th Birth Anniversary of Mahatma Gandhi (02 Oct 2018)
200 Years of Paika Rebellion (24 Dec 2018)
Atal Bihari Vajpayee (Special definitive on 25 Dec 2018)
Mahamati Prannath (25 Jan 2019)
Vedanta Desikan (01 May 2019)
Jallianwala Bagh Incident Centenary (13 Apr 2019)
Maharshi Mahesh Yogi (30 Aug 2019)
Master Healers of AYUSH - Maharishi Mahesh Yogi, Vaidya Shastri Shankar Daji Pade, Vaidya Bhaskara Vishwanath Gokhale, Vaidyabhushanam K Raghavan Thirumulpad, Rajvaidya Shri Brihaspati Dev Triguna, Swami Kuvalayananda, Hakim Md. Abdul Aziz Lakhnawi, Vaidya Yadavji Trikamji Acharya, Dr. Dinshaw Mehta, T. V. Sambasivam Pillai (30 Aug 2019)
Accessible Elections (Election Commission) (MyStamp 13 Apr 2019)
Queen Heo Hwang-ok - Suriratna (30 Jul 2019)
International Labor Organization Centenary (22 Jan 2020)
50th International Film Festival of India (MyStamp 20 Nov 2019)
150th Birth Anniversary of Mahatma Gandhi (1869-2019) (02 Oct 2019)
50 Years of Commercial Nuclear Power – Tarapur (MyStamp 28 Nov 2019)
Guru Nanak Dev (550th Parkash Utsav) (09 Nov 2019)