Back when West End Games was still making Star Wars material, in fact producing much of what would become the building blocks of the Expanded Universe cannon, various authors requested material from the game source books to help spin their creative writing juices.
One of the first authors was Timothy Zhan.
I'm not sure what the actual details were at the time, but there were a request for "any information on Bothans".
West End Games "they delivered the Death Star II plans and location to the Alliance. A lot of them died."
Timothy Zhan, "Right. I got that. Anything else?"
West End Games, [search, search, search] "We got nothing."
Timothy Zhan, "What do they look like? Are they human like a
Corellian?"
West End Games, "Umm ... Well ..."
Timothy Zhan, "Ok. THANKS. I got this."
Illustrations for the Heir to the Empire Sourcebook from West End Games show them as fairly Human-like creatures with fur. The Heir to the Empire comic depicts the Bothans differently, as largely fur-faced with long snouts [almost akin to Joe Camel the mascot of Camel cigarettes, something many of us in West End games did not like at all].
The Shadows of the Empire comics follow the lead of the West End Games sourcebooks, as do the Shadows of the Empire Planets Guide , Star Wars: Rebellion , the Star Wars Customizable Card Game , and the Databank [this last source uses the image from the card and was the main image for some time]. Meanwhile, long-snouted Bothans appear in later EU games and publications.
Finally The Essential Guide to Planets and Moons shows Bothans as an average between the two extremes.
Man, I'm old.
Now you fanboys get off my lawn!