1. Consider providing a 'status' of the money tipped, so people know the artist actually got the money and they didn't send it into a blackhole.

2. Dogecoin is a must - shouldn't be too hard if you have Bitcoin already. The communities are very different.

3. Services like Tinkercoin allow you to buy a small amount of Bitcoin with credit card. Consider adding this info for the fans to get a small amount of Bitcoins.

4. There are some musicians in the space who are big into Bitcoin, like Tatiana Moroz. You can contact them to promote your site in the music and Bitcoin communities.

Good luck!