On the three Stack Overflow chat servers, the chat room not available page displays the following image:
Is it from an actual episode, or is it a 'shop?
Definitely photoshopped. Worf's sash being silver and not frayed cheap table-cloth-material gold makes it at least 2nd season, but the uniforms make 3rd season or later.
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The simplest way to check this is to go to http://startrek.com and look at stills for ST:TNG episode summaries.
I don't remember all the details, but after the first (or second) season Patrick Stewart threatened to sue Paramount because the one-piece jumpsuits were so tightly fitted they put excessive pressure on their shoulders and spines. There was an initial change to respond to that issue, then another later change. While I wasn't able to tell, off the top of my head, when the changes were made, I went to http://startrek.com and checked stills in episode summaries to verify the uniforms. There's one style in 1st season (the all-in-one), it's changed for 2nd season, and in 3rd season and alter are the simpler collars without the diamond shaped shoulder "pads," just as seen in this image.
I'm re-watching the series at the moment, and I think I have found the scene where that image was originally taken from:
This is in the teaser for Deja Q - and the reason they're all looking in different directions is that an annoying high-pitched noise has started on the bridge, so they're all looking for the source. Turns out, this noise is heralding the arrival of a very naked Q.
The hats are most certainly shopped in - as for the rest of the image, the more I look at it, the more it seems to be a composite. Picard, Riker and Worf are all looking in different directions - which would look a bit silly on TV, although this could just be a momentary thing.
It's also possible that the photo is a promotional image - it has that kind of look to it.
I've tried quite a bit of google image search, and cannot turn up anything that could be the original (the problem is - there are so many shots of these three on the bridge).
Still - judging by the uniforms, I'd say this is probably somewhere in season 3-5 - so if someone is watching these at the moment, they might spot them.
The hats are likely to be a reference to Firefly -- Jayne's hat from the episode The Message, although the colours aren't quite right.
I couldn't speak for the rest of the image, although even without the hats, the expressions do seem a bit odd, don't they?
Photoshopped. To me, it looks like Worf's and Picard's hats are the same, while Riker's is mirrored and then edited a bit.