I know you're trying to help. But it does cause a little unnecessary confusion when you try to answer questions with wrong information... (not that there was actually a question here.)
As for giving out wrong information... I placed a picture in a post and had the post removed (by a moderator?) because it was over 400x400. (no, it was not a singature pic)
Hmmm... without knowing the specifics, I can't say why that would have happened.
But the size limit is for signatures. You'll find lots of folks using photos in posts here and there that are larger than that.
It is true that posting large photos (pixel-wise as well as byte-wise) may not make you a very popular poster with those using dial up connections or smaller monitors...
We just need to remember that lots of people are using dial up connections, and large photos mean that a page can take a longgggg time to load for them.