I've created a new BootSkin (nearly ready to upload to WinCustomize - just wait a few more days!).
The files that make it up (the background, progress bar, and ini file) come to about 150KB.
As well as this, most of the .bootskins available on WinCustomize seem to be between 10-100KB.
However, when I selected "Export selected skin to file.." in BootSkin I ended up with a .bootskin
file 2.32 MB in size. Any ideas why?