Planetfall
I like Planetfall too, but it seems like all the themes that I like have problems. They're all from third parties, volunteers, archived at the tikiwiki themes site.
Frank's been trying to find a consensus for a theme to use. When (if?) he does, it'll be worthwhile for me to put in the time to fix it. There's a nonzero chance that fixing it will require making specialized changes to the HTML produced by templates, which may make the adopted theme incompatible with other tikiwiki themes. So you can understand my caution about committing to a theme until we're sure it's what we want to live with.