I make handmade pendants and logo design and sell them on Etsy ([link]). It takes 0.20$ to list an item which will stay there for 4 months and then, you have to renew it. Etsy also takes a commission when you sell your item. It's hard to get known because there are a lot of artists there.
I'm there since 6/7 months and have sold only one product. But i'm also in another French webshop which is free to list an item, they also take commission when you have sold one product. I have a lot more buyers there than on Etsy because there are already a lot of jewelries like mine on Etsy but not on the other website. (The other website is A little market [link]).
There is also Dawanda but i'm not there. You have to make some promotions by yourself if you want to get visitors, also posting in forums, etc...
Just remember they charge you to post ($.20 I think) and take 30%. So make sure your price is high enough to cover that.
You can just treat it like a gallery in that respect, which you expect to price at about 2X what you sell to them for. Put your price there at twice what you NEED to make to cover that art. So if you'd charge $20 for time and materials make it $40 for the site.
What to charge and what you can sell depends on you and the media. Probably the best thing to do in your case is to browse the site for a while and see what people are selling similar products for, then tweak the price as needed.
I personally don't like etsy. It is incredibly hard to get your work out there in my experience. If you've already got a good following on other sites it shouldn't be to bad, but otherwise you run the risk of having a very hard time and repeatedly paying fees on things you never sell.
I have an Etsy shop and I love it. [link] I think the best way to determine price ranges is to look up other shops on Etsy that are selling similar items and look at what they're charging. In terms of what to sell, it's important that you shop has a cohesion to it, I frequently see shops that are too diverse, which confuses buyers. If you have other questions, let me know!