yes you can download them all now and then go back later and add boarders and such.
I downloaded all of mine right away and then nd of forgot about them until I got an email from Disney saying my pictures were going to expire. Then I was like, oh crap! and I went back on and decorated a bunch and downloaded those and made a photo album.
When you download it makes a copy for your computer, all the orginals are still there. So technically you could download them al to multiple computers by logging on and then downloading on that computer.
They don't start disappearing until 45 days after they are taken - so you have time to play around with them.