The file size limit for uploading images has been recently increased from maximum of 1MB to 2MB. However, there were some issues with the auto resize of the pictures by the forum software as soon as the images were 4 to 5MB. As a result, images needed to be resized first in other sfotware before they could be uploaded.
I contacted Wouter and he has extended the maximum size limit again to avoid the manual resizing of picture. As a result, it is now possible to upload even larger images. Check out the latest Pontiac threads (example GTO 2nd gen) for some B&W pictures in full glory (5,5 MB quality size). Hopefully, this will not be a problem for the servers long-term, I only report what is possible at this moment Wouter is aware.
I only needed manual resizing when pictures were 6 to 7MB or larger and even then a simple save in lower quality (95%) with Irfanview was sufficient, meaning the size of the image was not decreased.
Thanks Wouter for your support, if there are any further issues or comments regarding file size they can be put in this thread.