I have tried to register my methods like this:

[InitializableModule]
public class ResizeTest : IInitializableModule
{
private bool _eventsAttached = false;
public void Initialize(InitializationEngine context)
{
if (!_eventsAttached)
{
DataFactory.Instance.CreatedContent += MyTestEvent;
DataFactory.Instance.CheckedInContent += MyTestEvent;
DataFactory.Instance.CheckingInContent += MyTestEvent;
DataFactory.Instance.CreatingPage += MyTestEvent;

_eventsAttached = true;
}

}

public void Uninitialize(InitializationEngine context)
{
DataFactory.Instance.CreatedContent -= MyTestEvent;
}

public void Preload(string[] parameters)
{

}
void MyTestEvent(object sender, ContentEventArgs e)
{
//do something here
}
}

Doing so, the only event I am able to trigger(through debugging) is CreatingPage, when I try to create a new page. As explained above, I want to do some processing on images after they are uploaded. When reading the SDK I get the impression that CheckingInContent or CheckedInContent are the correct events to listen to. Am I doing something wrong?

Solved with :

UnifiedFile.UnifiedFileCheckedIn += MyTestEvent;
UnifiedFile.UnifiedFileCheckingIn += MyTestEvent;
UnifiedFile.UnifiedFileDeleting += MyTestEvent;
UnifiedFile.UnifiedFileDeleted += MyTestEvent;