People are brainstorming new logos for Mastodon in this GitHub issue:
https://github.com/tootsuite/mastodon/issues/962

I really like the direction https://github.com/SamSaramyak's is going:

@blinry I like the big cuddly current image, partly because it sets masto completely outside tech branding.

Why does it need a logo that makes it look like it was inspired by StackExchange?

@blinry Wait, I got it. You mean an alternative to this thing, right? I mean, sure, I don't even know what the heck that is supposed to be.

Seeing as the fediverse is supposed to be all about celebrating local identity, why not default the logo to blank and let instances supply their own? Even without one, nothing important is missing -- branding isn't a thing and apps supply their own icons anyway.

@mrb Jep, that thing. When I first saw it, I thought of a mammoth trunk + tusks, I think.

People in the linked GitHub issue are also thinking about customizable icons, yeah! :)