There is no simple way... You can set up additional albums and move some pics to a new album. To do this, set up the album, the find the pic to be moved. Edit the pic and you will see an option to move it to a new album. Not exactly easy but easier than reloading images.
You have brains in your head. You have feet in your shoes. You can steer yourself any direction you choose | Dr. Seuss
The fact that this site is sort of low-tech and clunky is part of its charm! Sort of a neighborhood feel, rather than corporate. So if I can't rearrange my photos, no big deal -- at least I get to hang out with my buddies!