Sorry I didn't see this sooner alladin~
I would do a search for public domain photos and you should get a lot of pops there. Or search for creative commons licensing say on flickr, etc.
The important thing to remember is that the images need to be 'allowable' for commercial usage (because we are on hubpages it is commercialization of the images). Public domain do not require attribution but I always state they are public domain images.
The others need a link to the picture - just copy the address and note the source in the appropriate spot in your capsule.
The best way to avoid any trouble whatsoever of course is to take your own digital photos and upload them!
Hope that helps and good luck on the hubs!!