I think a fun option for tremulous would be to have custom skins and emotes/dancing taunts that are earnable for a build up of enemy kills. I believe this would add a fun element to tremulous. (note these skins would not add any buffs to anything all of this would be for looks.) For example a skin requires 30 kills throughout any number of games to unlock the skin and then you can wear the skin and have a feeling of what to play for in the long run to earn skins/taunts. 
ranks might be cool to!
Test Server already contains the ported Quake 3 model functionality - but it wasn’t designed to function with equipables and the textures bug out as a result. This function does not work for the alien team.
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Aside: Murnatan will have user-definable as well as purchasable character/weapon models & textures, but not until beta/release.
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The way the light armour and the helmet were implemented in trem is by shaders/textures. We have been using custom models that were previously made for Quake 3 mods years ago to test the 1.3 custom model system in development. In order for the light armour and helmet to not look distorted and weird they would have to be reworked to fit each custom model, but in lue of that, we are making use of a generic camouflage texture for custom models in general, which is not ideal but it works for now. The custom model system can work for the aliens, but we don’t have anby available custom models at the moment that would function for them.
As a side note, the system does support multiple skins for a given custom model.
Ultimately we would want additional models/assets made specifically to fit with Tremulous for both teams, in terms of both appearance and function. We don’t plan on including in Tremulous releases the custom Quake 3 models we have been using to test the system, only custom assets designed for Tremulous would be included, but server owners could choose to make use of their own custom models with such a system. This custom model system is intended to offer some perks for obtaining higher karma in regards to the planned karma system. More information about this system can be found in this topic:
I do like the idea of adding to the system custom taunts that could be unlocked, that would require making additional animations for each given model though. It mostly comes back to making new assets.