Sorry Tahtus, I did not put explanation I had in before. Basically, there are several units that did not recieve different appearance with the veteran, guard, imperial upgrades which do now.
Matthew - no worries buddy. I think everyone knows imperiosis is behind the extra "fantastic" artwork.
I think the xpack "additionally" uses not just stuff in datapx.bar, but the stuff in art4.bar as well, which is what I assumed. I will uninstall expansion pack just to be sure (but those would be the contents that differ from vanilla - janissary has different tag attack so it will not work with both versions of the game - thus I left it out)