Hi, I have a picture entity which contains the key, content type, filesize etc, and content (a byte array). How can i make the byte array lazy load using the self-servicing template?

That's not supported, unfortunately.

Could i say, create another type specifically for the content, and have that added on to the picture entity? (So its seen as a related object, not part of it). Can THAT be lazy loaded?

Yes, in a 1:1 relation you mean? (MainEntity 1:1 PictureEntity) that can be lazy loaded indeed