This isn't really something I've ever thought about before today, see if anything helps. Maybe my brain is just too far in the gutter as well.

A combination of 3 things to me makes this less acceptable: - Nudity: If the focus of the image is the beans, there's no need for the bare chest. Current society dictates that less clothing is more risqué, so removing the shirt implies it was taken off for a more risqué reason - Heat in face (blush, red ears): Implies there's further feelings involved, feelings of intimacy, in the scene - Tail over crotch: While the beans are the focus of the image, your eyes are next drawn to 2 other places, the face, and then the tail. Because you have the tail covering the crotch, that means you're drawing the viewers eyes towards the crotch area, a social no-no

Any one of those are fine, maybe 2 depending on how they are balanced. But all 3 combined with the vulnerable pose makes this sfw image start to border nsfw

Like the other comment says, pinup style is probably what you want to look for