Hello,
zipfile worked quite well, except it didn't have a directory inside, but that was easily fixed.
The graphics look nice, for as far as I understand what they are for.
It took me a few days to understand why you made those graphics, as they don't fit with the other gui graphics, but I now think I understand. Your idea of how it works is probably different from what I implemented.
Looking at your images, it seems that you assume a fixed size background for a window, which some small areas that can change. This is however not how it works.
Starting with the widgets (roughly the interactive standard buttons, area, labels, etc), all widgets of the window are built from small parts. A rectangular widget consists for example out of 9 sprites. Four for the corners, four painted repeatedly to covers the sides between the corners, and one painted lots of times to cover the center.
See the graphics/sprites/gui/GUIEles2.png file in the source code. The idea behind it is that the contents of widgets can change in size, eg a user wants a different front, or use bigger graphics, or switch to a different language. Fixed size rectangles will invariably be too small. It has to be dynamically sized instead.
While the sprites in that file are currently very simple, there is no particular reason why they have to stay this simple.
As you may have seen, coding the widgets is behind w.r.t. the available graphics. Eg there are full graphics for a scrollbar, but the code cannot draw one currently. On the other hand, there are also widgets still missing. A tab-page could be useful.
Last but not least, there are a lot of small item graphics badly drawn or missing. There is no 'delete' icon, no compass graphics, etc etc. The code does it all with strings currently, which works, but it ain't pretty. For the coaster build window, I made some bad graphics.
(I am also not convinced that flat 2D style bends are the best possible graphics, but I cannot do better.)
As you can see there is plenty of stuff to work on.