spacing / padding around partner logo element when displayed as a grid

although you have the grid the different “images” are placed in a slide-loop and the slides are numbered – starting at number 1 from left to right – to to bottom : slide-loop-1, slide-loop-2, slide-loop-3 etc.

so you can address the “image” via that class – why i do note it as “image” these are background-images – no img tag here !
So a padding will not bring you to your wanted result.

but try f.e.:

#top .avia-logo-grid .slide-entry-wrap .slide-loop-6 .av-partner-fake-img {
  background-size: 80% !important;
  background-position: center;
  background-color: inherit;
}

if you want it for only that element – give a custom ID or class to the partner-logo element.
e.g. with my-custom-class

#top .avia-logo-grid.my-custom-class .slide-entry-wrap .slide-loop-6 .av-partner-fake-img {
  background-size: 50% !important;
  background-position: center;
  background-color: inherit;
}

if you use a jpg for that slide – change the background-color to the background of that jpg.