I decided to integrate the sun glare/screen dirt shader that was posted a while ago in the resource section on garagegames.com it makes things a bit shinier.
For those who do not like it, I added it to the graphics settings so it can be switched off if desired.
Additionally I integrated it into the postFX manager system, so it can be individually turned on or off for each level. I did this mainly to avoid an error that caused a crash when loading a level without a sun flare, but Azaezel helped me to solve that as well. Maybe I will finish the integration into the postFX system later with adding the variables into it as well, so users can tweak it individually, it may be wise since the effects vary from level to level depending on the lighting conditions, sometimes it is too strong, sometimes barely visible, but for now there is a good compromise in the settings.