It's implied that people are looking at pictures of 2 people getting it on. We do not see these pictures.
Throughout the series we see several pieces of art with some nudity though not graphic or explicit.
In the very first show they show you a deceased girl in the morgue and you can see one of her bare breast.
No explicit nudity, murder victims rear ends can occasionally be seen however hard to see as they're often in the dark and covered in blood.
Infrequent nudity in the series. Some bare butts and silhouettes of nudity, but it's heavily shadowed and/or out of focus. On broadcast TV, all nudity was censored though on streaming and DVD/Blu-Ray (most) nudity is uncensored.
Season 1: No sex scene at all. One kiss scene.
Season 2: 2 sex scene. Some kiss scenes.
Season 3: 2 sex scene. Some kiss scenes.
There are also sexual innuendos, some nudity and sometimes sex is talked about but this show has actually very few explicit things. The sexual/sensual intimacy and tension in this show are more mental and psychological than physical. It's very artistic.
There are two women laying on a bed, one of them is mildly naked. No explicit nudity. It is implied that they had sex.
Two murder victims are found deceased and semi naked in a motel room. Their bare backs are visible and nothing else as they are dead and layed on the bed. No buttocks or breasts or anything else seen.
A woman is seen in a bathing suit before she jumps into a swimming pool. Nothing else is seen.