The usual cause is filesize being too large.
This is why I ask for the image, because without seeing what it is you're attempting to upload, I can't exactly tell you why it isn't working.
So if you can't email me the photo, or give me a link to it (if hosted online somewhere), there's very little I can do about it. Most people know how to attach an image to an email, I try to make this as easy as possible.
If you email it to me, and it is too large, I'll either fix it, or just add it to your account anyways, even if it is outside of the specified limits. We're really not that fussy about it.
If you can spare a minute to send it to me, please do so, the problem will be resolved in a matter of minutes.
