Post your photoshopped coins! They can be edited in any way, but be sure to add a disclaimer that actually altering a date or mintmark on a coin is illegal. WARNING: Only do this with Photoshop or some other image editing program. Actually altering dates and mintmarks is illegal.
Do filters, cropping, etc. count? lol I think those would mostly fall under the realm of "sound" practice, despite the fact that they may be edited via PS, Gimp, etc. Conversely, adding or subtracting "matter" as opposed to lighting or cropping would be a different story. In the example shown in the original post, I see that as "ok" to do on an eBay listing as long as the original non-PS'd pic is included, too, though I wouldn't do that. Anyway, I don't recall PS coins on eBay besides the addition of arrows to point out where the seller is claiming the errors are. Those are plentiful even on, esp. on the Errors forum, so I won't post those pics.
The mint did not scrap plans for a 1995 Abe Vigoda commemorative upon finding out that he was actually still alive.
Pretty much all of my pictures get run through the shop... This one, however, is NOT photoshopped, except for a circle crop:
Not my images, but these are from an ebay dealer who seems to work on his coins to make them look "nice". The first is his worked up image of the full coin, then the second is cropped from his image of the slab, which appears to be un-modified.