I'm currently reading the walking dead on my kindle using the hidden image viewer. its hidden cuz it's not perfect, but a much better solution than having those margins.
I just converted the images from the .cbr of the comic I downloaded to greyscale 600x800 PNGs. Once you have that you compress them into a ZIP (or a CBZ, they both work) and put them into the documents folder on the kindle and it will show up like any other book.
Only issue is it doesn't keep metadata (like book cover and author info) so it looks a little ghetto on the kindle. Once you open it just hit menu and enable fullscreen viewing, there's no bar on top or status bar at the bottom. It does remember where you left off, but the viewer is a little glitchy. Works good enough for me tho.
Hope that helps.