Are you loading JPG-Images?
Because they're very memory-consuming, may you should also take a look how much memory your application needs, since this can also lead to slowdowns.

To your question:
If you're using view entities, I think tilt won't work (but I'm not sure about that). Why you don't span them as regular entities and setting the tilt?
If you use ent_create, make sure you create them at a xyz-position which is visible in the camera. You can press the "0" button in debug mode and move around the camera to see where your entities are created.

Regards
TSGames