for attaching a banner- see if you can find a way to rig it up with string or twist ties onto hooks or the little railing on the edge of shelves, etc. In our room we'll ask the steward to leave the drop down bunk out so I'm hanging dd's birthday banner to the bed rail with small zip ties.
I hadn' thought about the static cling decals- if they're using them on the big portholes off the artium why not try it in the cabin?