Everything within bounds of reason. No one will be endlessly correcting an item, however, in certain situations it is possible.
You can see the difference in shading on the example of Memory Box. I remember that Honourable Knight of Honera was not satisfied with the first version of his design and after some time it was corrected.
https://tibia.fandom.com/wiki/Memory_Box
Midnight Panther Doll get some effects after using the item.
Golden Newspaper in it's first version has much slower animation with sparks and only in a "+" shape.
Note, that the only person who may ask for any change in graphics is admin of the fansite himself. Item creator can not ask for any corrections.