If you're using the MAME artwork packs on an arcade monitor, it's imperative that you enable artwork_crop in your INI file.
For an extreme example, check out Space Invaders. The backdrop artwork is huge. If you don't crop it to the actual screen area, the game isn't really playable on an arcade monitor.
Try these settings in your INI file...
#
# CORE ARTWORK OPTIONS
#
artwork_crop 1
use_backdrops 1
use_overlays 1
use_bezels 0
use_cpanels 0
use_marquees 0