Although it looks good in some parts like the "Continue" screen or the "Options" menu, others feel half-assed, like the Bag and Summary screens. In the Bag case specially it looks like tha bag was simply given a negative filter, and the darker colors of the summary strike too much with the brigth ones, like the lime green that you put as an example.
Overall its a good idea but feels like you didn't fully commit to the idea of a darker theme, and rellied on either a negative filter or putting a semi-transparent black image on top to make the images less bright.
I could suggest you to try narrowing the scope of the resource, leave things like tilesets and battle graphics aside (since players are mostly going to change those anyways) and focus on UI graphics more commonly used. Quality over quantity.
Also if are going to use colors use the darker variants, like a wine-red, deep blue, etc. Has potential but needs some more work.
Yes, you're right, it was cobbled together fairly quickly!
When I next get round to working on this, I will make use of your recommendations.
Swdfm