the bg needs more work, it looks like you just took a pic of the stadium and that's it.. experiment with textures, gradients, brushes, stocks++ and try to make it look smooth

stocks often look best desaturated and on low opacity (try different layer modes) and textures look good both desaturated and in original colors (again try different layer modes).. if you use brushes keep them simple and don't overuse them!
colors needs improvements, the bg is too colorful and the render needs more colors

tone down the bg colors and work on them so that they match the render colors, and add a hue/saturation, a contrasts and/or a levels layer to the render to fix it
render also needs more work, experiment with some simple but cool effects to make it more eye catching and make it stand out from the rest, but don't overdo it

and remember to blend it, if you need help on this we have some great tutorials
text is ok but you could easily make it look a lot better, get some new cool fonts in our resources section, change the colors of it and use some VERY simple effects on it to make it a little more interesting

and remember you want the render to be the main focus point of the sig, and at the moment the bg is..