French copyright laws are, as I understand it (and, mind you, I am not an expert) much more lax than American copyright laws, meaning that images fall into public domain much faster there than here.
This means that there are tons of wonderful images across the pond that you may use in your own work (or at least be inspired by them.
A wonderful site that features a wide variety of images is Agence Eureka.I love this site.
I imagine that a collage artist would find a lot here to use to layer in their work.
From old cinema glamor shots to scans of kitschy packaging to wonderful wildlife illustrations, you'll find it all....
For me, I am most interested in the ideas for fun paper toys that were published once, long ago. If that kind of thing appeals to you, then be sure to check out the category on the right for "cat. découpages." In this case, découpage has very little to do with mod podge and a whole lot to do with fun things for kids to cut out and assemble.
There are little jointed animals that move when you pull a lever, dioramas, little cars to glue together, games a whole ton more.
Of course, I'm in love with the mechanical toys, like those I assembled at the very bottom. As the instructions are in french, it is often a bit mysterious as to what these toys do until after it's all assembled but that's all part of the fun.