A letter box, cork board, key box, shelf, trivet, 2-tile tray, or frame. The base for a wire basket, a magazine box (six tile mosaic here!), a metal trivet/frame, a napkin holder (kinda tacky) or a rack to simply hold your tiles for use as coasters.
Many suppliers offer the wood products in alderwood, rosewood, and black. Some are available unfinished so you can stain or paint them as you like.
Here is a list of suppliers I have located on the Internet who offer reasonable prices and carry the items pictured above. Just make sure you purchase products that will work with 4.25" tiles as other sizes might be available.