Velcro

When our Airstream had carpeting (ozite) on the walls, we used Velcro hook self-stick tape to attach things.  Just stick it on the back of a decorative badge, a picture, a router, a modem - whatever - and stick it to the wall. 

Now that we have removed the carpeting, we could not give up Velcro.  Here we used it to attach a lamp to our table.

  Just be sure you select a good aggressive Velcro - preferably from a hardware store.