I'd pass that banner by if I saw it somewhere. The composition is very weak, it doesn't grab me at all. Worse, the pixelated look makes it look like you either don't care or don't know how to make an image look good, which does not say good things about the comic.
Focus on strong visual elements in your banner. Learn about composition. Use these things to improve both your comic pages, and the banner. At present, both are rather boring because you're just drawing the characters/events without thinking about how you can use the overall composition to help convey information/tone.
Consider the colours you're using. Are you sure that a plain white background accurately represents the tone of the story? If you're going for blood-on-white, then make the blood more white. It may be more realistic for thickly pooled blood to be dark, but it doesn't suggest "blood" as well as a brighter red would.
Try to use the same style of artwork in your banners and other advertising materials as you do in the comic itself. False advertising, even when it's minor like this, tends to be a turn-off for readers.
This is a bit of a nitpick, but try to avoid situations where you have identical glyphs (letters) next to each other in fonts that are meant to look hand-written or otherwise organic. It looks artificial. In words with doubled letters, like "doll", modify one of the letters. Some professional fonts meant to look handwritten offer multiple versions of each letter specifically for these situations.
On the subject of text, I know this is getting off-topic, but please put more love into the lettering in your comic. The font you're using is hard to take seriously, Comic Sans is pretty much the stereotypical "this is an awful comic" font, and you might be losing potential readers just by using it.
Your text is also arranged rather poorly, the text doesn't
sit comfortably in the bubbles and the bubbles don't
lead the eye in the right order in some cases.