just thoughts
skins - just popped in my head, though i know it would create a bigger installer thus depicting the soul purpose of packing small installers
links - ability to have active links in LicenseData or in the BrandingText
exe search - ability to search for an exe file and then make it as the install directory (or did i just miss how it is done?)
logos - BGGradient could have the ability to handle not only texts but also graphics (or active links even)
make offline - i bet it is a great help if you could make the NSI Online Template Generator available offline
browse - ability to change the texts in the browse window, the one that appears when searching a folder to install the application
spaces available - ability to read actual available space, not just 1GB+, and perhaps also add another one that reads the size of drive. thus completing the 3 common components; size of disk, spaces available, and spaces required.
< Back - disregard this button in the lisence page rather than make it unavailable
multiple disks - multi volume installation files so as to be able to distribute them in floppies; and option to choose the file size per volume
uninstall options - so as to select which items should only be removed; the same as the repair function in the microsoft installer
eof