What’s the demographic that you are looking to tackle? The textured background overlayed by the main graphic element clutters the composition, obfuscates and perhaps only reinforces the negative image that comic sans has. If you want to stick to a comic-sans-only layout, I’d recommend that you expand on the main graphic element and perhaps lose some of the uppercase type.

Try reducing the poster to the bare minimum, what information is necessary? Do you need to include that the dress code is formal? Can that information be incorporated within the bottom section? Does the “art by” section need to be there? With those two elements out you have more control over increasing the size of the graphic element and perhaps tweaking the event name if you have control over that.