Google for Mother of Pearl tiles, either make or buy the mirror and mosaic the frame. Very easy to do.

Oh, I don't think this would be difficult at all. I think the hardest part would be mitering those tiles perfect like that. I'd probably try squaring them instead. If you glue the tiles tightly together, it doesn't even look like you'd need to grout it.

If it were me, I'd start with a sheet of plywood cut to the ultimate size of your mirror (including the tile border). Have a glass shop make a beveled mirror to the size you want. Or if cheaper, find the mirror first then cut the plywood to the size of the mirror plus the border. You want at least 1/2" plywood to be sturdy enough.

Glue the mirror to the center of the plywood, then glue the tiles around it. Just make sure if you do end up grouting it, you tape off the mirror to avoid scratching.