You need to use codes to resize and change the number of frames used in GFXs.
There is a thread in the help and support forum thatcontains all the NPC codes. Also for animated objects you need to put each frame on top of each other like this

You can't do anything for BGOs and blocks and need to be the same size as the original (For BGOs you can make the visible smaller than the original though the GFX must still be the same size) unless you are using PGE which should resize those for you.