[restructured from the conversation on #alientrap]
I think it's a good base but some of the elements in the gui need clarification. If we're speaking in terms of usability, I'd say it's a step backwards.
Scroll bars, sliders and checkboxes, all lack contrast and definition against the background. This can be confusing to any user, new or old.
The checkboxes, the buttons and the inside of the main window are all square, which makes it a bit boring. Sure the insides of the buttons have some interesting details but the game type buttons are obviously stretched, something the 2.4 default theme hid pretty well. I'd go as far to say if this is going to be the new standard theme, it requires a code change to give game types a different background, otherwise it just looks bad.
The selected map has a white background, which make white text with a black shadow hard to read.
I think the
blue theme is a better starting point but the contrast of the form elements must must must change.