It will be a problem with the main Sling server, where remote controls are linked with remote images. Even if you report it I suspect Sling won't do anything about it. I recall from a few months back that Comcast insisted that the Motorola 3416 always show their Remote and Sling just rolled over and did it.
Assuming you don't have a Slingbox 500 (where Sling have removed the functionality), I can probably help by buildlng a Custom Remote for you. I would need a picture of the remote image you want. Maybe by installing a different (non-working) Cox remote ? In fact I see from doing a Forum search (I assume you did as well?) that the Cox DCT-6416 might work and give the right inage ?