This screen shot is typical for many logo pages in presentations:

Images files are copied into the slide after which a background shading is added. The shadow creates an instant frame around the logo which is too tight, definitely not the framing the logo designer intended. Now that all logos have a box around them, the eye immediately wants everything to be distributed and aligned properly in a grid, which is impossible to do given the different sizes of the boxes. Finally, the drop shadows actually do not look good.

My approach to logo pages is to adhere to a strict grid and keep everything on a white background to give the logos space to breathe. In PowerPoint or Keynote it is a bit fiddly to line up all the logos, I usually put in a temporary table to make sure everything is lined up in rows and columns. When every logo is in its place, I delete the table.

My presentation app SlideMagic makes it easy, it is impossible not to align images in a proper grid.