Thanks for getting back to me.
I think I understand that but have no idea how to do the css for that.
I obviously do want it to look good on mobile and at a good size, but I also want it to work on a screen i.e to resize so I don’t have the background colour showing.
I asked woothemes about it and they said to put my add images as custom logo but I can’t then see how that will give me a different image on each page…? They haven’t responded to that.