Well actually, for imageshack, I'm not 100% sure if they allow 7mb images or not, but I do know that always get upload failed if I try anything that big, so I can't get it working anyway.
Each image you upload must be less than 1.5 megabytes in size. If it is greater than that amount, your image will be optimized for internet use.
That second quote is from the imageshack FAQ, so yeah, they have a restriction.
http://bayimg.com/
Seeing as that site has a 100mb limit, I tested it out, but when uploading my 7mb image (no problems for small images), after it seems that the image has been uploaded, I just end up with a blank page and the image fails to upload.
I'm not sure if the problem is with me or the site.