No, you can use them, just try not making them overly HUGE in that they destract others who are trying to navigate a post.
Usually, if they are too big, I'll edit the image size properties on my end. My access and HTML limitations are better then the normal users default config, so I can add code to resize the image. Usually though, I won't give a rats ass unless someone else complains to me about it. Then I'll usually, just kindly ask you to replace the image with a smaller one that is less destracting.
So far though, I've only had to ask 2 people to change the signature pic because of the size.... I think Royal Orleans was one of them, I don't recall, captainfrenchfry's is kinda big, but it doesn't destract too much. I'd probably limit myself to just about that size if I were you. Possibly smaller.
ALSO, your signature is not showing in posts, because you have not made 25+ posts yet, it will appear soon after, even though you have it made up in your UserCP.
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