Who can apply branding to a branch?
A Console admin, or a user with a custom role containing permissions below can access the Look & Feel option to configure branding:

• Manage Branding

• Read branches
• Update branches 
   

I want to apply the same branding to branches within my hierarchy, do I have to configure it for every branch?
No, uploading the same branding is not necessary!  Simply apply the branding you want to the top level branch.  The branding will cascade down to all of the children branches.