In the spanish forums we use the system of 3 different images when we remove any avatar... so the user at least have some idea on why the avatar/sig has been removed...
1. When the filesize is too big...
2. When the image is too big (in pixels)
3. Bad content
Same story when we remove a signature...
Firma retirada por rebasar el tamaņo permitido (Filesize too big...)
Firma retirada por superar las dimensiones permitidas (Image too big...)
Firma retirada por contenido no admisible(Bad Content)
EDIT: Im not sure if KeyStorm or Choli coded that... still...it works just fine...