Promote Community on my KF Server

Hello, i have some questions about ads:



Can i put some ads on my servers?, promoting my community that also offers servers for rent, so the players near my location can play without ping or delay.



Also can i edit some maps and put graphic ads on walls or some sort of less invading adverstising on my kf servers?



I ask this becouse i dont wonna have any kind of Copy Right problems, so any answers or alternative suggestion are welcome.