Modding a ROM - Problem with icon size when installing APK

Hello,

I try to mod a rom but I have this problem : I've added apk in /system/app.
After the boot, if I open the applications view, siome of them use little icon and some other normal icon
Launcher used : JB launcher2

Any idea to have the same size for all ?

By the way, if I install an application thru the Playstore, it is the same problem : it will have small icon

Thanks