The reason those collages look so good is they have a unified look…so unify yourself! Go around your house or to a discount store and pick up an assortment of inexpensive frames.
Use a sanding sponge to scuff up the frame. lay out a big tarp and some pvc pipe or dowels. Lay the frames on top of them.
Use your favorite shade of spray paint to spray a unified color on all of the frames.
Roll the dowels back and forth to make sure you have the frames completely covered and you don't have any sticky pooling around the edges.
Allow the frames to dry completely and frame up all your favorite photos. Use some matting on some of the photos to give it added depth.
Then, hang your frames for a great look at a fraction of the cost. I'm Mrs. Fixit and it's just that simple.