As I'm building a forum software, I'm racking my head over this problem lol
As it turns out, the more professional / usable themes also tend to be the most boring themes.
My first three themes for it are along the lines of throw something fun and unique together.
The fourth and fifth are intended to be more professional. All five have the status of default theme, but the fourth is the defaultest default.
Two is being decommissioned, it's a fork of the first which didn't really work.
Three onwards were written completely from scratch much like the first theme.
1: Tempra Simple.
2: Tempra Conflux.
3: Shadow.
4: Cosora.
5: Nox.
There were three experiment ones too, but they were scrapped as they kinda sucked due to too many compromises.
The first three have rotted and probably should get some fresh life injected into them due to the attention Cosora snatched away from them, plus I was a little sceptical about the attention on them.
I probably could do something interesting again or to reinvigorate those, but that might have to wait a short while lol
A logo can improve an average look and maybe a few exotic colors. So in that case, you could just buy a regular theme.
That's what they do with sites running Discourse. It still looks the same lol