There isn't really anything new in version 1.9.1 of TrayBlank - all the real changes are more external.
First, there is now a 64-bit version. With something as small and simple as TrayBlank there shouldn't be any difference in performance between 32-bit and 64-bit executables, but it shouldn't do any harm either. The main reason I compiled a 64-bit version of TrayBlank is because I want to produce a 64-bit version of JPEG Saver - which is likely to be a lot more complicated and so I wanted to try it out on something simpler first.
The second major change is that I've used the WiX toolset to produce .msi installers instead of using the NSIS-built .exe installers I have used previously. This should make it easier for me to build installers that put the 32-bit and 64-bit versions in the right places, deal with upgrades correctly, etc. The downside is that .msi files are quite a bit bigger, being a kind of database file instead of a self-extracting executable. I think it's worth the increase in size though.
As an aside, having now used both NSIS and WiX to build installers I can safely say they are both awkward and unpleasant to work with. WiX does give me more confidence that things are going to be installed and uninstalled correctly though - a lot of validation happens when the installer is built, so it is harder to produce one that doesn't work.
The new installers and zip files are available from the downloads page.