Here is a beautiful Craftsman/Mission style picture frame and tile frame. Each corner has square blocks using mortise and tenon joinery to attach the stiles and rails. To secure each corner block round dowels are used from the back only so they're not visible in the front.
Dimensions: The picture frame is 8x10 with the outside dimensions being approximately 11x13.
The tile frame with tile is 6x6 with the outside dimensions being 10x10.