Is there a way to reducing the size of the airplanes/liveries (aircraft selection and liveries)  in the main control panel world Map?

 

thanks

Probably not in the main sim as that will be in the core code. But all the livery designers are doing their own thing when it comes to how these are displayed in the sim, which is a pity. You can fix that though, there are some packages that have the liveries in the correct (Asobo) standard and you just replace the two jpg files with them. At least then all downloaded liveries are presented uniformly and not a mishmash.