Here's a quick list so you know I'm thinking of you!
1)Have a good reason for any exception. I'm placing this hear as a first rule because each and every suggestion has this as an exception; you can do anything you want, as long as you have a good reason for it. Keep this in mind as you read each suggestion, and you should hear in your head a lot of times!
2) Diversity is key. I don't mean this in a strictly racial sense; you need a variety of powers and weaknesses. Each character needs to have their niche and speciality; a character that can be outdone by another character is going to be useless. By the same token, a common weakness is going to take your entire team out of action, and that's annoying to readers (not only is it basic manipulation, but it's going to ask the question of why aren't they taken out more often).
3)Avoid cliches, but don't run from them. This is the hardest thing to deal with; you're going to want to create something that's unique, but you can't avoid the basic cliches because they work . The obvious one is Spandex; from a practical perspective, they are help you market the characters, and, well, let's get real: If you had super-powers, and had to use them in combat situations, you'd either go armor (which also helps market the character), or in something that covered you while being comfortable. Spandex does that really well. And, better yet, your super-genius can make it into something that either mimics powers or is otherwise unaffected by them (useful for that character who is covered with acidic slime!).
4)Have fun! I can't stress this enough. Too many writers forget this, and so get burned out quickly. If you aren't enjoying it, then no one else is either. At the same time, don't do something you don't want to do simply to make your comic something more popular or profitable; ironically, that will almost always make your it less popular and harder to profit from. Follow your heart, and hope others will follow.
5)Always have someone with glasses. A personal preference, but I find that groups that have at least on character with glasses and/or goggles is much more interesting than one without that accessory. But that's just me...
1)Say that there is something you won't do. This limits your characters and your plot, usually artificially, and that's not a good thing. A lot of fantasy stories don't have elves; by advertising that, they may be favorites of elf-haters, but they usually replace elves with something similar or that takes their niche. Obvious stupid question: Did they actually eliminate elves? In the super-hero genre, you find comics that don't have costumes, secret identities, or world-shaking abilities; what fun is that? It also prevents you from have to be an apologist later on if you decide to introduce the banned subject. Don't do it in the beginning, and you won't have a problem later on.
2)Think that you require a pantheon. It may help to build your universe, but it's not necessary. You can have a character that is the only super-powered being, or at least the most advanced or experienced. For that matter, he could hunt down other powered characters. But don't think that you need a team that handles all of the heavy lifting; that can be just as limiting and harder to write.
3)All characters need powers. Consider Iron Man; he has no powers, and yet is able to keep up with the other Avengers. Batman? He's won every fight against Supes. Don't feel that you need to have every character having powers in order to have a great comic. Even Naruto has Rock Lee...
4)Avoid common origins. Although it irritates a lot of people, having a common origin liberates you in a lot of ways. You don't need to keep everyone's origin straight, you don't need to allow for different mechanisms, and you can leap straight into the story. And it gives you an excuse to have everyone join up and fight someone if the secret is to be revealed or if that common origin is threatened. This isn't to say that you need a common origin, just that you shouldn't avoid one because you were told that it sucks.
5)Obey the rules. It's your story! Not anyone else's; they aren't responsible for writing or illustrating it, and they don't know where you're going with it (if they do, there's problems!). Just remember that if you're going to break or bend them, understand why the rules exist in the first place.