There is also a size limit, I'll check it out and let you know. If I remember correctly was somewhere around 2.5 - 3 MB max.
Also only JPG. PNG and GIF. Only those formats are supported.
They have the copper membership activated, read the OP and see the Profile
EDIT:
As I thogh it is 2.5MB See this quote and check the guidelines there :
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Bear in mind that the maximum size for an image (file image size) on this forum is 2,5 Mb, so if you decide to recreate your original file to allow for a better resolution and size, you will be subject to this file size limitation.
This thread may come in handy:
GUIDELINE ON POSTING IMAGES (WITH SIZE ADJUSTMENTS), HYPERLINKSLet me know if you need more help.