Head to your local craft store and check out the wooden plaque aisles. You could also make your own if you had access to a jigsaw (and a steady hand). Likewise, you could simply use two frames of different sizes, paint them different and then stack them together.
Blissfully Ever After: DIY Photos on Canvas. She used an actual photograph, trimmed to just smaller than canvas size. Mod podged photo and pressed onto canvas. Used black paint - dry brushed sides and edge of photo and added a triangle of paint onto each corner. She mod podged the entire photo after paint was dry. This is the result.
Put foam board covered in fabric in a large frame. Love this idea for pictures want to temporarily display, like ones that just got printed. Wouldnt dent the pictures or make them hang funny like the clothesline frames do, but would look more like a bulletin board. Would use double-sided tape to hang the pictures.