I can suggest three solutions:
•The first is to set the new frames with SetObjectImage() each time (provided that you have single images)
•The second solution would be to set the UV coordinates via the meshmemblock commands to shift through the atlas image.
(Can't find inbuild UV commands for objects.. a shame)
•The last solution is just to set the UV/Texture coordinates via a Shader.
hope you know what i mean ... anyway feel free to ask me anything about the methods.
You can get single images like so:
SourceExplosionImageID=loadimage("Image/Explosion.png")
global ExplosionImageID as integer[16]
for ID=0 to ExplosionImageID.length
ExplosionImageID[ID]=LoadSubImage(SourceExplosionImageID,"img"+str(ID))
next ID