How do I transfer an unlockable gamer picture from the Xbox One to the Xbox 360?

You can't.Gamerpictures on the xbox one are different than those on the 360 & wouldn't work anyway.

This user is talking about the gamer picture in the game Banjo Tooie for XBOX Live Arcade. Unfortunately the gamer picture you're talking about can only be unlocked once and as far as my knowledge goes gamer pictures unlocked cannot be downloaded again if
they are tied to achievements. If you wanted that gamer picture you'd have to get it from one of the gamer picture packs that are on the marketplace located
here. I believe one of these picture packs includes one of the pictures that you unlocked
by completing the game achievement.

Hey there, do you have an Xbox One at all? The picture at the top right of the web page is generally governed by your Xbox One gamer picture.

My picture does vary between 360 and Xbox One, but mostly it's the Xbox One gamer picture. If you don't have an Xbox One then I don't believe there is a way to change it.

Hi there,

I think you are referring to the gamer picture, which can be an picture of your avatar, but also some other icons are available, you can set this via the xbox console (360/ One)

See this link on how to do it for the 360:
support.xbox.com/.../xbox-gamer-profile-settings

or via this link to do it via a PC:
live.xbox.com/AvatarEditor (When silverlight is installed)

Hey hi, I read that you had trouble finding your gamer pictures but the question I wanted to ask you is: How did you buy them? I can't do it and it gives me an error when I want to buy a pack of gamer pictures, where did you get it from? Xbox 360 or PC?

just buy them on the website or on the 360 console. but you need to have a xbox 360 to download them and put them on your profile unfortunately, the 360 emulator for xbox one and series x/s doesn't show the ones you own so you have to get on a 360