We have a wonderful community for providing help to users of construct but what you are basically asking for is someone to design a game for you or to do all of the work for you from what I am understanding of your post.
When creating a new game generally you want to get the game mechanics working first. Most of my games the player is just a square that moves around and I do not worry about the art until I am sure I have something that I want to invest artistic time in to.
Based on the image you provided you could put together a fairly simple version of that type of game (I think you are thinking of "Last Stand / Last Stand 2 flash zombie games).
Remember always start small, get a player image up, it can literally be a picture, a circle, a square, or anything else. Provide movement for it, add in some behavior(s) and then after the player object moves in a fashion that you like you can expand on that by adding some kind of firing projectile mechanic etc.
If you need help as you go with individual problems or ideas on how to approach features please feel free to ask. The community is very helpful, and there are some seriously talented people that will be more than eager to help you through the process. But if we do the work for you, how will you ever learn and get better?