whonix is modified debian or built from it , so whatever works there it should work as well inside whonix.
as u know accessories left for the user to choose which one he needs to install or not.
so u will have to install what u need inside whonix.
if u need something works as Photoshop inside whonix, then u need to have gimp. and to install it:-
open Konsole -> then type:-
sudo apt-get install gimp
then Enter (type ur password) then press y the Enter = finish.
if u want to open it:-
go to the blue K on the left down side of the screen then type on the search field at the top
gimp then open it = have fun.