Email signature on iPad (or iPhone, for that matter)

I have successfully loaded a .jpeg and/or a .png into the signature settings on my iPad for a gmail account using my apple mail (for working at home), but the image does not appear when I send an email.

I then checked using a plain email signature and no signature is attaching when I send an email on a yahoo account.

Then, I checked my jpeg signature in settings and it disappeared from the gmail account setting.