Perhaps fix the varied colours on the transport_bg (and add toolbar_bg with the same color)?
I attempted this myself, however I still have rather annoying rgb(49, 49, 49) outlines around elements as seen. I've been unable to locate the source of that... but it's an improvement.
It'd be much nicer if it was just a solid colour with text, or if there were proper delineators for the elements.
The default just sucks.
(I attached the transport_bg.png for this, and I simply duplicated that as toolbar_bg.png as well to make the main toolbar blend in with the transport.)
Almost had it looking right, but the time signature box turns black anytime I add/change transport_edit_bg.png. transport_group_bg.png changes add black bars on the side of it.
edit 2: All working.
No more ugly rgb(49,49,49) lines. Just a smooth seamless transport and main toolbar.
So I had to create the following files with a full value of rgb(43,43,43)
Then remove the line "set trans.curtimesig.color [. . . . 43 43 43 255]" from rtconfig.txt. This seems to cause issues if transport_group_bg.png and/or transport_edit_bg.png are provided.
Even if my idea isn't accepted in to the nitpicky theme, something needs to be done about the transport.