I'm not sure where you want to go so I hope its OK if I just drop my two cents.
I have recently played with compiz which is amazing but actually just a fun way to waste some time, not the KISS way, though I don't see any reason to not post themes/artwork for compiz since its available for TC.
Usually I prefer minimalism over fancyness but I also prefer functionality and/or visually appealing themes which, at the same time, do not distract me. F.e. I always disable the Themes service on WinXP but I don't do so on Win7 where I'd loose some functionality.
Shortly before my TC4.7.7 USB installation died, I removed lots of icons from the gnome-icon-theme, hoping to reduce the ballast by eliminating which I found to be ugly anyway (several MB that was, I think). Might be nice to have a lighter replacement.
I got used to use Fluxbox which is easy to create themes for I think (I edited an existing one which nearly suited my taste). While JWM or FLWM are functional, they are ugly as hell by default (which scared me) - these might need nicer themes.
I don't like wallpapers. I usually set my background to just black. Actually I just found out today that Fluxbox has some nice backround features so I made my 'wallpaper' to be a dark gray grid on black background.
fbsetroot -foreground rgb:0C/0C/0C -background rgb:04/04/04 -mod 16 16added to ~/.setbackground
"hsetroot ..." commented out.
I like the TinyCore logo a lot. Though as it has been said, visibility is not that good on dark background.
I always prefer my PC to boot quickly. Boot Splash is not for me.
I'm even using logo.nologo boot code. Not sure though if it has a significant effect on speed.