Type /callvote in your console for help.
maps available for voting are:
q3dm2
q3dm3
q3dm4
q3dm6
q3dm7
q3dm13
q3dm17
maps are called by typing /callvote vstr
here are the map cycle names and voting strings:
for q3dm2 you would type /callvote vstr dm2
for q3dm6 you would type /callvote vstr dm6
for q3dm17 you would type /callvote vstr dm17
and so on...