I suspect that my suggestions might not work but (because they're both related to possible causes of your problem) they fall within the category of 'first things to try anyway'
1. Check that Outlook hasn't disabled to automatic display of images in HTML messages. (Actually, you should have that setting enabled anyway, as a necessary security measure):
Try right-clicking on the box with a red 'x' in it to see if there's an option to download the image.
Also go to Tools > Options > Security and check that there's not a tick against 'Don't download pictures or other content automatically in HTML email'; if there is, remove it. (If there's no tick there it might be worth putting one in, closing Outlook, restarting your computer and then removing the tick again; I've no idea why such things work but they have done for me occasionally!).
2. Check that the problem isn't with your email provider's server:
Log into your email account via webmail (i.e. NOT with Outlook) and take a look to see what mail has been stored on their server. If it's at the absolute maximum the server won't forward images to Outlook. Delete anything which shouldn't be there.