Meta clients can have a custom logo next to their auction on both Google and Tripadvisor. Here are the requirements for adding your logos on metasearch.
Google:
Dimension: square - at least 72 px up to 1,200 px
Format: PNG
Background: transparent or non-white
Text: no more than 3 text characters (no more than 3 letters or numbers)
TripAdvisor:
Dimension: 384 px x 164 px (WxH)
Format: PNG
Size: 6kb (min) - 12kb (max)
Background: transparent - logos should be optimized for white/yellow backgrounds (#FFD14F)
Border: No additional borders around logos
Depth: 32 bit with non-boxed logo against white/transparent background
Text: the logo should not contain any call to action or marketing text