The satellite imagery layer visible on Mapillary’s web and mobile apps will be temporarily disabled for maintenance purposes. We aim to introduce a new satellite imagery layer as soon as we can.
If you need satellite imagery layers in the meantime, we recommend viewing your imagery in iD Editor using the Mapillary photo overlay.
Best,
Said
The satellite imagery layer visible on Mapillary’s web and mobile apps will be temporarily disabled for maintenance purposes.
Well, in my understanding this temporary maintenance is long over. 
Anyway, since serving satellite imagery on a website surely demands some considerable fees, it is understandable that finding some suitable replacement is not that easy. However, website visitors may not be obliged to pay license fees. Hence, I would like to suggest that for now, you add a URL option layer so that Mapillary users can at least make use of their favorite imagery provider. While at it, you could also add a projection option as a bonus because many free of charge open data imagery providers (usually government organizations) use proprietary projection parameters (often with aerial imagery) best suited for the geography they cover. However, for now the web default projection EPSG:3857 would be better than nothing.
By the way, what is the update cycle of the “Mapillary streets” layer? Imho it is a bit slow and somehow inconsistent too. Some tiles seem to be more often updated than others. Yet others maybe never.