If you’re looking for some quality sprites, then look no further than Magnus Noctem. Unless otherwise specified, these are RMVX sprites. Note: Unfortunately, this site is no longer being updated, but it still has several resources and resource links on it.
You can find some Mack RTP Sprites here.
Or these Sprites With Portraits (includes some for RMVXA).
Alternatively, the Mystical RTP Sprites, which is one of my favourites.