You can upload your own profile picture/avatar for your Linktree. You are not tied to having the exact same image as your social profiles.
Uploading a new avatar
To upload your own avatar, you need to be logged in to your Linktree admin. Then go to the Appearance section in your Settings tab and press the 'Upload Avatar' button.
From here, you can upload any profile photo you want. The photo dimensions will need to be 180px and under 1mb in file size.