Well, you asked some tough questions, esepcially for a non-expert such as myself here, but I will do my best to help you out!!!
One of the first things I noticed reading your comics was that you did spend time on the backgrounds -- which is great!! Since they're not as fun to draw (or look at ^_^) a lot of people don't bother much with them.. (Of course I am guilty of that too T_T) But anyway, I can see that you try to put em in, and more importantly, try and make the character *fit* in them, like showing them from the same angle and stuff..!!
Stuff like here http://stevesan.topcities.com/mangastri ... shed10.jpg
or just in general through out the comics!! It looks nice, good perspective with a character matching it.. I'm surprised you are asking for help, when you are a lot better at it than so many others!!!
But, if its still really bothering you, you might want to consider that its not the backgrounds, but the charcter designs that make you feel that way. Don't get me wrong, I love your art, its soooooo cute :D But what I mean is that your characters are sort of SD-ish, they don't have exact proportions, so they don't might stand out a little bit in a realistic BG. So you might want to try experimenting at drawing the characters' proportions and entire bodies.. But still keep em cute, so its a hard balance >_< This stuff isn't easy!!!
A really good thing for backgrounds is that if the setting changes, try and include the new background right away. If you have people talk for a while without showing where they are, its sort of disorienting. And if you do this, you can just draw one good background at first, and then not worry about it when you're trying to show a character's expression with funny backgrounds ^o^
Another general good tip that may help is to just sketch out everything!! Visualize what you want, draw a very faint suggestion of the character, and then build in a background, then add details. A lot of people just start from the face and work outward, but if you do that, you are leaving too much up to chance!! You have to figure out where each piece of the picture will go before you go and draw it! (Your drawings don't really seem to have this problem though, but it does seem like you put the most work into faces and backgrounds, so try setting specific relative heights and proportions for all the characters... Or something like that!!!^_^ Your bodies are good, like here: http://stevesan.topcities.com/mangastri ... inji23.jpg
so keep it up :D)
I hope I don't sound down on your drawings, cause they really are great!!! But, everyone has some room for improvement... I am even more critical to my own drawings!!!!! >_< But, its the only way to improve!!
As far as story goes, its always important to plan ahead, even though its one of the hardest parts. Just like you should sketch out a page, you should plan out the story to some point. You don't exactly have to come up with the dialog for the next 20 pages or anything, but it helps a lot if you have an idea of where you want to go with the story and characters. I had this problem a lot before, where I would come up with good characters and an initial plot.. but then nothing for them to do after they are all introduced ^_^ So I would just stop drawing after a certain amount of time. If you plan things out, it takes a lot more time to prepare, but it makes it a lot easier to write, and helps to keep you from "burning out" after a lil while ^_^ Like.. Its easy to come up with a character and have them have an interesting past, but its hard to think of a plot to bring that aspect of them out.
But anyway, being inspired a lot is a good thing, if I only I had the problem of coming up with too many good ideas ^o^ But I think if you plan ahead a bit more, it won't sort of "replace" the other stuff you are working on, but instead you can work on both!!!
Anyway, I love your comics, they are really cute! Too cute to be left half-finished!! Work on them!!! XD I think they have so much potential, you should spend a lot of time working on them!!!
Ah, wrote too much ^_^;;;; Trying to sound like an expert or something ^_-;;; I am the worst at advice!!! *dies*