Anything larger than 800x800 will be auto resized by the forum software.
Another option is to add them to the photo gallery and link them back to your post here with thebutton.
If you have them hosted somewhere else you can link them with thebutton also.
Photo gallery is the best way to view big events.
If someone wants to upload a ton of pictures to the gallery I can have you upload them to the sever via FTP and process them for you.