szurkebarat, 808Studios,
While not a perfect solution, perhaps the following little command can be helpful in this case:
perl -ni -e 'my $l = $_; chomp($l); print qq($l.$_\n) for (qw(jpg tif))' FILE
Replace FILE with the name of the selection file and extend the list (jpg tif) with any other file types you like. Th command will replace each line in the file with copies, but now with the listed extensions added.
Above command is for use in the Mac OS X Terminal (and instead of type in in the FILE, just drop the file from the Finder in the Terminal window).
If you're on windows, the command should work with just a small change (and of course, any version of perl installed), I haven't tested this though:
perl -ni -e "my $l = $_; chomp($l); print qq($l.$_\n) for (qw(jpg tif))" FILE