I've always wanted to incorporate it into a mural or graffiti. Or car paint.
There's a Gibson novel, I think, where the protagonist at some point obtains t-shirts with a pattern which is recognized by the universal DRM-enforcement code in video camera chipsets, making them invisible to surveillance.
If refusing to process/print Eurion marked things was a legally required feature (which it currently isn't) in printers/image processing software, it could pose quite a conundrum for OSS, if the law also requires that the feature not be easily disabled by an end user. It's hard for me to imagine OSS software with this property. Yet the law could demand it, and society might find it reasonable.
Unfortunately, imaging systems co-evolved with humans, thus they tend to hack things so that they are sensitive to light in the exact way the human eye is. (Your monitor isn't emitting orange light, it's fooling your eyes by making it think the light is orange by activating red/green/blue-sensitive chemicals in your eyes the same way orange things do.)
Digital cameras can be pretty sensitive to IR, but there is typically an IR filter over the sensor to prevent detection.
One cool trick I learned was how you can take a normal remote control and view the IR light flashing when looking at it through your mobile phone camera. It's useful for determining if the batteries are still good in the remote, for example.
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