We ALWAYS decorate our room!!! Here are a few tips......
Visit the dollar store for affordable decorations you don't mind leaving - Halloween and Christmas ideas are fabulous.
We always ship down a box in advance....warning.....convention hotels will charge you to do this. We generally stay at BWI (BWV next time). To get around this, we spend our arrival night at Riverside -- and see BOB the first day.
Pickup "Contact" hooks and tape. These are designed to be applied to the wall....AND are easily removed without damage.
At Christmas, for example, we had a small tree decorated with lights and flowers from the Dollar Store ($12 total), GIANT snowflakes hung on our balcony along with a Santa windsock and snowman flag, lights on the balcony railing and a christmas door cover on our door.
Halloween - we had "Head on Hildie" <--- $1 witch that looks like the flew SPLAT into the wall, blinking eyes on the glass doors - goblins all over our walls in the room.
Friend's birthday at DL - giant birthday door banner, birthday sign on the balcony of the Grand Californian, silly plastic streamers and lights on the balcony railing, room filled with birthday silliness - birthday banners, signs, had balloons delivered to the room.....so much fun!
It's just part of the Disney fun for us now!