I've overlooked the transparency setting. The transparency level is great, just a little bit too much grain imo. 

Basically, I don't need themes - just a little more settings to match my desktop theme. Mainly looking for a way to get rig of the light grey. To have a "dark" theme (dark background/light fonts) on everything, not just the active tab.

The following settings would be great:

Active tab color, 

Active tab font color,

Non-active tab color,

Non-active tab font color,

"Background" (bar) color, 

Slit up in focused/non-focused. Maybe a general focused/non-focused setting would work well, that makes everything a bit brighter if not in focus.

And maybe:

customize buttons (close, menu),

transparency level (for active tab too),

grain level (and maybe some grain/noise textures to choose from, or load your own),

and size. (height)