jpeg image does not show in background

[Piscium]

I got a jpeg image from the net, set it as background, and it was not
shown. I converted it to png and the png was shown fine. I am trying
to find why jpeg background is not working (I do have insmod jpeg and
insmod png).

Googling I found this ubuntu bug that includes a patch:
https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/541670

The author welcomes pushing upstream, but as the bug is not even
assigned, I assume that never happened (I searched this list archives
for "huffman" and there was no recent message).

I know nothing about jpeg. My question is if there are known
limitations on the types of jpeg file that can be read by grub2, and
if so, what they are. I am using v. 1.98.