I think I don't need to explain that running a modded server is only for experienced users and verygames can't give any support for it, since it's too different from the product they offer support for.
I am not completely sure how it works or if it works but you asked if it was possible and yes, when you choose minecraft openmod on both VQS or VQSi servers, you are able to upload a custom modded minecraft_server.jar. I don't think that more creeps would work on a server, but you can try this, there is always a risk though that the server won't start anymore and like I said clients need to run the mod too, besides all this, mods are made for single player and placing more monsters may place them for everybody on a different spot. There is another solutions for this all, it's called bukkit and this allows you to run plugins, notice the name change, Bukkit server is basically a modded minecraft server, which gives the possibility to run plugins. It is possible to mod your minecraft server, you don't have to have infinite, you just need to have minecraft openmod, just remember that mods are only made for singleplayer and may not work on the server at all, besides if they do work, you got to have every client running the mod too.
