You're right that depending on the image, some viewers might see some BDSM images as sexual assault. But I would argue that they fall into "explicit," although I'm willing to go along with consensus if most folks here think that BDSM should go into non-con.

We can edit the policy to say that BDSM goes into "explicit," and warn users who might find that upsetting to click on such images with caution (or not at all). The article text would often make it clear that the explicit image was BDSM (you can infer that from the "Men in Chains" article title and text even before you see the image, for example).