However I can think of three things that would affect the time that it takes to print BOD but there may not be much that you can do to improve the situation:
1) Transfer time. The time that it takes to transfer the Postscript file to the printer depends on the size of the file and the transfer speed. Graphics of any sort greatly increase the file size so they would slow things down. Assuming that you are using a parallel printer port connection, you probably cannot increase the speed much unless there is a better printer port driver than the standard Windows one or if there is a different BIOS printer port setting that would work better. I don't know of any. If the GEMS computer is networked you could consider adding network support to the printer which may or may not faster.
2) Processing time. The printer has to run a PostScript interpreter to convert the PostScript file into an image that it passes to the print engine. Different printers use different processors and some may be faster than others. It may be possible to get an expansion cartridge that would be faster but not that I've heard of.
3) Fuser heating time. In order to print, the fuser has to be up to operating temperature. However this draws a lot of power so the printer will normally go to a stand-by mode after a certain idle time. It then has to heat the fuser up again for the next job. It may be possible to adjust the idle time so that you are more likely to not need to wait for warm up between ballots.
All of this is theoretical. Tests could be set up to determine which of these is the bottleneck and the biggest performance improvement would come from addressing that problem but it could be a lot of work.
I hope that this helps a little.