"Actually, in dev mode, i get an exception if trying to load an image, the file doesn't exist on disk. This prevents me to load anything of the page.
Is there anyway to maybe change this to a warning or something like that?"
I understand why an exception is thrown. The real problem is the way it is caught or not. A 404 on an image can't generate a "500 error" on the page.
For me, it is the same problem than : https://jira.ez.no/browse/EZP-20782
We need a native exception handler.