Adjust your sig pic size:
Signature Size Limits
All signatures should not exceed the following size limits, and you can't have both text and images
* 500 CHARACTERS. Exluding image tags and code.
* Do not use images with large text to bypass the previous item
* For images in signatures: 1 image up to 500 pixels wide, 100 pixels tall and 20k in size for SN hosted images.
* 650 pixels wide, 125 pixels high for off-site hosted images
* Animated images in sigs are not allowed unless approved by staff