Do they make bullnose tile in these mosaics?

I'm pretty sure they don't make bullnose tiles but would have to double check. That would be a good solution though. As for the artwork, are you thinking framed art or more like a metalworks type of piece?

"Pencil" liner makes a perfect finish for backsplashes...it is usually about 1"w x6"-12" long, comes in a variety of colors and textures, is adhered just like tile and can be grouted in to match (available at Lowe's...etc.).

Thank you for all your suggestions!

i think the combination of pencil glass tile to finish the edges would be great. And as for the artwork that I referenced @akee36, I think you could actually do either... a little metal works piece or perhaps something long and narrow framed in glass. Try hanging up a cut out sheet of paper to get a sense of size. You could consider a candle sconce too in metal but that might look a little odd or out of place.