Greetings, Legacy!

Unfortunately, pretty much every major mod for Medieval requires Viking Invasion as well. You would be doing yourself a huge favor by picking it up, as it adds a lot of content to the game (besides allowing you access to all of the larger mods).

There is one exception, however. I believe Wes' MedMod (which can be found here) still has a version which is compatible with vanilla Medieval (although you still need the 1.1 patch installed). While I have yet to play MedMod myself, I know a lot of players have highly recommended it in the past. Along with BKB and XL, it's considered to be one of the 3 main mods that keeps the game in the medieval setting (as opposed to Hellenic TW and Napoleonic TW, which are "total conversion" mods).

In any case, I believe that's the only major mod you can download without having VI. I've heard it's a lot of fun, though (if somewhat tough), so you might do well to check it out. Good luck!