This is one of my favorite projects because not only is it easy, but it helps you take out some aggression with a hammer :)
So first, you need to get thrifty and find a mirror and some old plates that match your desired color scheme. (It's fun to recycle someone's old things! Trash to treasure right?!) I decided to pick up the fun colors in my bedspread.
*Make sure your mirror has a relatively flat frame and enough room for you to get crafty with plate placement. It doesn't matter if the frame is "ugly" because you will never see it.
After you get your materials, put a few plates at a time into a paper bag. *For your safety, make sure to wear work gloves so that you do not cut yourself and work goggles to protect your eyes just in case. Next is the fun part, HAMMER TIME! Check periodically to make sure you are smashing the plates to the desired size for your mirror.
After you have all of your plates smashed and ready, use grout mix or mosaic tile mix to apply the plate pieces to the frame of the mirror. I usually place the rounded edge pieces of the mirror around the edges so that there are no points around the edge.
Let dry, and TADAaa!
Another tip, *If you don't like the white grout, you can use tea bags to stain the grout to an off-white color. This is really great for antique style mirrors. Also, you can add beads, antique brooches, etc;
The options are endless and no two mirrors will ever be the same!