Coinsandcanada.com

When I try to upload some bank note pictures, I get a warning that the file size is too large. What is an acceptable size?

Here's from the user's guidelines:

Can I post images?
Yes, images can be shown in your posts. If the administrator has allowed attachments, you may be able to upload the image to the board. Otherwise, you must link to an image stored on a publicly accessible web server, e.g. http://www.example.com/my-picture.gif. You cannot link to pictures stored on your own PC (unless it is a publicly accessible server) nor images stored behind authentication mechanisms, e.g. hotmail or yahoo mailboxes, password protected sites, etc. To display the image use the BBCode [img] tag.