I like the layout better in Yuku then in Aimoo, but you can't put backgrounds in there and the ads are awful.  The group I am in is now paying not to have them.(some of the members donated money to help pay for ad free).

In Aimoo you can put backgrounds.  It's a bit to set everything up, but it is workable.  I haven't experienced the ads in Aimoo yet.  You would be able to put alot of what you have here in this forum.  From what I understand you can have them migrate your group, but it gets archived and isn't usable. 

I am also interested in FreeWebs or the new name for it is Webs.  It looks like their group section and layout might work very well for a group.  They actually have over 300 layouts.  I think the only way I would be able to find out what can and cannot be done here would be to make a group and try things out.