It's basically the same as selling in the usual places. You would need to put in every information a buyer needs like what you're selling, how much? the countries you're willing to ship to, their pictures, condition etc... the only difference is your audience are mostly skeptics (for a good reason!) so you should probably clear any potential doubts. This is also why asking for donations doesn't do well here unless it is started by a reputable member.
I would suggest:
1. Adding a note which contains bitcointalk + your username + today's date when you take pictures of your paintings. This is to prevent they aren't stolen from someone else.
2. Use a reputable escrow/midman which is good for both parties as it prevents scams, see this list:
₿ LIST ₿ Bitcointalk's ESCROW providers: Ranking & Blacklist ☠ Avoid Scam ☠As a newbie, you won't be able to post pictures but I'm sure the next jr member+ poster would help quote the image links for you.
You can just edit this post or start a new one.