1. like you said changing the surrounding to a different places. makes him feel that nothing is wrong in the surrounding but than create spikes around him.
2. by double layering the surrounding so that if the opponents breaks the first genjutsu he may not notice that his still under it's effect.
couldn't think other than this senseiU_U
Youd be able to change subtle things that can severely alter a battle. If you are fighting on a plateau you can make it so that its larger than it really is so that they fall off. You could change an exploding tag on the back of kunai into a string or something else.
See what I mean?