The only right answer is "we don't know." because no one at the hotel bothered to ask or explain it.

But based on the behavior of the angels in "The Time of Angels" there are two possible answers:

1. They didn't last long enough. Note that the video image of the Weeping Angel did not immediately turn into an angel capable of attacking Amy; it was only after the video had been on repeat for a while that it began to manifest. Similarly, the angel in Amy's eye manifested slowly, lasting well into the next episode without taking her mind over. In other words, we don't know how much time it takes for an image of an angel to become an angel in its own right. The images from the hotel may simply have gone away too fast.

2. They weren't really images of angels. This requires us to interpret the warning very literally: an image of an actual Weeping Angel will itself become an angel. Note that the image on the video, and the image in Amy's eye, were both images of a previously existing angel that was captured in the image. We don't know if the images from the hotel were images of real angels, or simply generic "computer generated" images based on their descriptions. It's possible that the images from the hotel simply didn't count as "images of an angel" on a technicality.

The only right answer is "we don't know." because no one at the hotel bothered to ask or explain it.

But based on the behavior of the angels in "The Time of Angels" there are two possible answers:

1. They didn't last long enough. Note that the video image of the Weeping Angel did not immediately turn into an angel capable of attacking Amy; it was only after the video had been on repeat for a while that it began to manifest. Similarly, the angel in Amy's eye manifested slowly, lasting well into the next episode without taking her mind over. In other words, we don't know how much time it takes for an image of an angel to become an angel in its own right. The images from the hotel may simply have gone away too fast.

2. They weren't really images of angels. This requires us to interpret the warning very literally: an image of an actual Weeping Angel will itself become an angel. Note that the image on the video, and the image in Amy's eye, were both images of a previously existing angel that was captured in the image. We don't know if the images from the hotel were images of real angels, or simply generic "computer generated" images based on how Gibbis saw them in his mind. It's possible that the images from the hotel simply didn't count as "images of an angel" on a technicality.