Hello @marcelita, Any image you own, any image that is yours without copyright restriction, can be used. These images will be a resource for collage creators. If it is art that can be used, that's fine. If you look at some of the images in this post by @quantumg, you will see that he created wooden fences and a door. These are his creations that he offers to the library.
I hope this explanation helps. I will try to answer any more questions you have.
Thanks for participating in our LMAC library-building effort.
Gracias por la explicación, ya entendí!