Well, you can do whatever you'd like, right? I got stuck on the Three Year Rule. <grin>
I think that asking for two designs is a bit much (okay, a lot too much). If your legs aren't done, save one the concepts for your leg. To me, it's like asking a chef to plan two menus complete with a tasting menu before you decide but only paying for one menu.
The other thing is to ask your artist, conceptually, which idea would make a better sleeve.