Throughout my house I have a lot of photos mounted to foam board, I love the look and I don't like trying to match frames or having a bunch of different frames but mostly it's so inexpensive:
Print your photos (or use old ones)
Find your local print shop that does the mounting. I use a blueprint shop that most architects use. It's apx $3.00 per mount, of course the bigger the pic the more expensive but only like a dollar or 2.
You can choose the thickness you want and even between black or white.
Here are a few pics I have from my engagement that I have hung above my bed. I use a type of sticky back Velcro (command) so it doesn't ruin my wall!