Still very beta, but here we go:
SPAM.PK3 for OpenArena

From the OpenArena FAQ:
... The installation is nearly the same as in Q3A. Simply copy the .pk3 files (of the map/model/etc) to your OpenArena/baseoa/ directory* ...

When it´s done simply start with:
openarena +map spam
or if you aren't familiar with terminals, once started openarena, bring down the console ( `-key for me ) and type "/map spam". With "/team s" you can join spectators. Bots are supported - i mean if desired, go to the menu (esc-key) and select "add bots"...

* Linux and the like: ~/.openarena/ Mac: ~/Library/Application Support/OpenArena/
Windows: %APPDATA%\OpenArena\

ps.: btw the idea is not all original. it's like the 3rd "kitchen" map i've ever encountered.