Easy DIY bunting- hot glue or sew lace to burlap. For an added "pop" - stamp a heart or lettering on the burlap.
Paper cave: I think ceilings are underused for interior decorations. Would love to try some more colorful paper or plastic cones on our ceiling. It would also be a great way to add too a "man cave".
Multi-Color Paper Swirl Decorations - Cut giant swirls out of poster board to hang from the ceiling