To create Bitcoin NFTs you need to use Counterparty, which is a community protocol on top of Bitcoin.
Created in 2014(with the burning of 2130 BTC, quite the opposite of an ICO), this protocol allow the creation of tokens with unique names with a custom supply choose by its creator. This was one of the first ICO platform with Omni, STORJ is an example of ICOs made on top of that platform.
From Rarepepe to CryptoArt
But Counterparty is a community project above all, and one of the best project made on top of it initiated the CryptoArt movement. This project is Rarepepe.
This project was started as a kind of card game for fun, with some emblematic crypto memes. Anyone could create a card with a meme and submit it to be accepted as a rarepepe card.
As Counterparty as a built-in Decentralized Exchange(https://xcpdex.com/markets) it was easy to trade those card, and a PEPECASH card was built and distributed to be used as the‘currency’ to exchange rarepepes.
As anyone could create this cards, some more artistics people started to propose their own vision of pepe, creating real art proposals, far from the first cards.
Among those we can mention MELANCHOLIA, PEPBOT,[To complete].
While Rarepepes had a lot of success, other NFTs collections were created on Counterparty, some with gaming intent like Bitcorn, Mafiawars, Memorychain, etc… You can view those collections on Book Of Orbs(Gplay or webapp)
Recommended: if you have Counterparty NFTs, try to play to Sarutobi Island, a RPG game where you can create your monsters(like pokemon) with the tokens you have in your XCP wallet 🤩
A little piece by Fred Wilson(from Union Square Ventures) who was quite fond of Rare Pepe movement … and later invested in CryptoKitties with USV: