Dynamic signatures

[Stryker1]

Hi, I have skimmed the rules and I haven't found anything about not being able to use dynamic images.
I just wanted to make sure if it is ok to use dynamic images (i am not referring to gifs).
Dynamic images are images hosted on websites that change the picture each time it refreshes.

Here is an example (reload the page until you get a different image):

 

[EpicNPC]

that's fine as long as the image height size remain 300px or smaller for all images.