Incorporating custom content

I am going to re-skin a flag into a time bomb, but all I know how to do right now is change all flags to that. How do I set it so ONLY the flag in my map is the custom one. Does it have to do with setting the "skin" in the properties? If so, how to I make the custom one I am making selectable with that process? Thanks in advance!

EDIT: How would I go about making it so a ticking noise is heard around the flag? Would it be an env_soundscape parented to the flag?

Damn. I wont be able to do this for a while then, since with the FIRST robotics competition, I have less than 25 mins of free time per day. I guess, now I'l start thinking about what a dirty bomb would "trail" behind it, like how the breifcase does paper.

On a side note, the VTF for the breifcase has a texture for the inside of the flag. I never really looked before, but next time someone plays (i cant for a while), tell me what parts of it you can/cant see. Thanks a bunch!