[neXXus`]

/*
 *   Votemap Delay 1.0
 *   by neXXus
 *
 *   Delays the ability to votemap right after mapchange in Natural-Selection.
 *   Prevents fastjoiners from votemap'ing another map right after mapchange,
 *   which would mean another mapchange, since they're the only person on the
 *   server at this time.
 *   
 *
 *   mp_votemapdelay - Sets the amount of time the ability to votemap
 *       will be delayed in seconds.
 *       Default: 60
 */

#include <amxmodx> 

It may work on other mods, too, with some slight changes (other cvar for ratio?!). You don't need this for CS, which has a built in delay.