Go to your
AdminCP ->
Skins & Templates ->
Images Only, find the images you want to hide and put this:
in front of the code
and this:
to the end of it.......... (that will hide them and if you ever want to show them again you can just remove the added code and they will show).
Alternatively you can just delete the whole code for the image you don't want, but then you won't be able to put it back unless you save the codes to another place.
Click on
Save Changes and you're done.