I printed up a bunch of these reproductions of my journal pages a few years ago and still have a bunch so I thought I'd see if they worked good for cutting up. They DO! and I certainly don't mind you cutting them up and using them in your journaling either. we sell them on www.teeshamoore.com.
and of course, we sell collage sheets too. I used them exclusively to cover some block canvases show here. Other sources of collage include copies of old journal pages, magazines of ALL kinds. You should know that I do not buy a magazine based on how good it is for collage. I buy ones that I like to read and then glean stuff from them. Also, children's books (with good illustrations) that you might find on the bargain table or at thrift stores. as well as other books at thrift stores. vintage postcard shows provide some interesting images that you can enlarge (most are way past the copyright laws). They usually have stashes of old photos as well behind their booths (you have to ask them). wrapping papers at those beautiful places like www.paperstudio.com are always great too.