The default folder DeskScapes looks in is C:\Users\Public\Public Documents\Stardock\Dreams. You can put them elsewhere if you like (for example to conserve space on your C drive) and then point DeskScapes to that folder- Open DeskScapes, Click on the round icon in the top left of the main window, click on "Folders" from the drop down menu, and browse to the folder from there. You could point DeskScapes to your generic "Downloads" folder, but it seem like that would get messy, it would probably be better to move them out of there. Yes you can copy them to another computer, again telling DeskScapes where to look for them if you don't use the default folder.
I think that's got it.