The designs are very nice, and I concur I too would be interested to reading your comic. Don't let the fear of someone stealing your ideas control what you do, go for it get the comic out.
An old trick I've heard is to mail the originals to yourself, leave the envelope unopened, the envelope is date stamped by the post office so if you can proof the date of your designs. Not sure if this would still be workable these in the modern world, I guess with postal automation you could send an empty unsealed envelope.
Although in this technological ages the images can of course be digitally and invisibly marked so that even after manipulation and conversion to different formats the image can be identified. I know of a company that has bots searching for these image tags across the web, then they send out demands for payment when their own images have been found. Good luck and if my advice has been helpful, design me an avatar that washed out smiley face to the left looks so sad !