Are you interested only in making levels out of ready to use porps, or also texturing, modelling etc. ?
Depends what you want to focus most on, if its map creation and level design, you should try unreal tournament, do some map remake for it. They have working game already, you can use some meshes and textures from other UT maps.
Here you will most probably get projects that have not much art done, so you need to create props. And projects that have done some models usually do have artist already.
For level design it is crucial to have at least movement nailed down, else you cannot be sure if scale of your map is right.
i have done some basic level stuff before. i haven’t tried rebuilding lvls from UT yet but that sounds interesting. i was hoping to learn both prop usage creation and texturing as well as prop creation.