Picture in Forum Signature

[Silencer711]

Hi all! I just tried to upload a rectangular, transparent PNG of my usual forum signature, but came up with the error:

"Your content can not be submitted. This is likely because your content is spam-like or contains inappropriate elements. Please change your content or try again later. If you still have problems, please contact an administrator."

For reference, this is the image ---> HERE

Thanks for everything you all do =)

EDIT: I couldn't even put in my other one;
// Steam //
// Nexus Mods //
// Twitter //