Why can't I save my image attachments from my email?

DataDigi here!

I have an iPod Touch 4th Gen with 16GB and I'm trying to figure out how to save images, like .BMP, on to my iPod Touch's Camera Roll from my email attachment. My people asked this for the iPad, but it seems to differ with the iPod. To detail things out, I am using the Mail App that came with the iPod, I'm using a Gmail account, and all the attachments I have are .BMP images on drafts. I dunno what to do, because it won't let me save them to my Camera Roll from the Safari App or the Mail App. When I tap and hold the picture's area on the Mail App, it gives me options like "insert picture or video" or "quote level" instead of "Put as Wallpaper" or "Save to Camera Roll". I don't know what I'm doing wrong! Someone please help!