Organizing and Sizing Contact Photos....

Just discovered groups and the icloud and organized all my contacts. Its so much faster to find something now.

Id like to add pictures to the contacts, just a few questions two quick questions.

Any suggestions on the most efficient way to add these to my iPhone so I am not stuck with a huge mess of pictures all mixed in together?

Id like to use the smallest amount of space I can for all the contact pictures, what is the best resolution and size to use?

Can I delete the pictures after I add them to the contacts? or will they disappear from my contacts when I do that?

Thanks