As crazy as it may seem to you, repainting may be something you should seriously consider.
Today's buyers want a house that is move-in ready and that includes the color of your walls! To you it is only a few gallons of paint and a couple of evenings -- but to a new buyer, it can be just too much more work and expense!
Especially if you have very bright or dark colors, it is really important to neutralize those walls. It will probably take a couple of coats of paint to cover those walls and most buyers are just not going to want to tackle that project immediately after moving in.
What color should you select? Don't go with white or an off-white. Select a tan or gray - something neutral but not bland. If you go with a tan, make sure it isn't a pinkish tan but more of a grayish tan. (It's best to check the color on your walls in different lighting.) Check out some model homes and see what color the builders are using. That is usually a safe bet.
And while you are painting the walls, go ahead and take down most of your pictures and patch the holes before you paint. You can re-hang some of your pictures but use those strips that are easily removed so you don't damage the walls. Leave any of the left over paint for the buyers, so they can use it to touch up any of the walls if they get damaged by moving their furniture into their new home.
If you have painted your children's rooms a good "kids" color, it is probably OK to leave them as they are. But if you start getting feedback from your showings referring to the "colorful" kids rooms, it is time to neutralize.
Wallpaper really needs to go. I happen to be someone who really likes wallpaper but I realize that I am in the minority. Just bite the bullet and remove any wallpaper -- it will really increase the value of your home and make it sell much more quickly. Really!
The goal is to allow the prospective buyers to be able to visualize themselves living in your house and you want to remove any roadblocks that will keep them from being able to do that.