I would approach it from an active approach, not a passive one. A passive approach is limited by the rules of electromagnetics in air, and as 2012rcampion pointed out, there's no real way to form an image outside of 5m without forming one within 5m as well.
However, active approaches are allowed to do far more interesting things. An active approach directly emits signals with an intent of confusing its opponent. This would not be able to make it invisible, but it could make it very hard to get a bead on.
All of the active effects you would be looking at would be "threat specific." They would have to identify a threat to them, and determine how their brain works well enough to find a way to mess with it. This creature would clearly have to rely on common patterns that show up in predator species, because it could never learn how to perfectly fool each individual.
Consider two situations that show up in fiction:
- An individual whom you are warned to never look in their eyes. If you look in their eyes, you'll get lost in them. That's when he strikes, and you wont even raise a hand against him.
- Looking in a mirror. Suddenly, and without rhyme or reason, the image in the mirror smiles and walks off, leaving you to wonder if you were actually in the mirror, and not him, the entire time.
Both of these seem to describe a visual effect which has a marked effect on the mind of the individual. This shows that there is prior art for visual effects disorienting an individual.
Anything along these directions would cause a tremendous instinctive desire to not look at the creature. As an example, we are constantly moving our head slightly. If the creature can "change its spots" in a way to make us think we aren't moving at all, by moving its spots in the opposite direction in perfect mimicry, we start to wonder if we have any control over our own body. If it can make a good guess (based on eye-line) to what part of their body we are looking at, they could blur those spots, and make everything else sharp, making us question if we can even focus our own eyes. That one would be particularly entertaining because the best way to look at it would literally be through the corner of your eye. (It would make it hard for the creature to guess what you are looking at).
A particularly self-aware individual could comfortably negate these effects. I find this to be a feature, because I find stories that reward self-awareness particularly interesting. A self aware individual could probably even choose to exhaust the creature by tricking it into using particularly exhausting patterns and movements, while the self-aware individual just smiles back at it.