Ideally we'd have at least 1 male, 1 female (where appropriate) normal representative of the creature, as well as more vivid versions too for "leaders". Some creatures don't have something easily seen as female, so like wolves we could really skip more than maybe 2. Some types, such as orcs, kuotoa, have subtypes, like orc priests of Gruumsh or those lightning clerics of the kuo-toa, or even drow sorcerers compared to drow warriors, which its nice to have a visual representation of too.
Richard M.
Grimfang"Whisper"Xaeraes