Once an image has been uploaded to Photobucket, it can easily be resized using the Photobucket 'edit' facility.
To resize an image in Photobucket.
Click edit above the selected photo in your album, (which should open the photo with a range of editing tools?).
Click Resize, check Keep Proportions, then use the resize tools to reduce the image size down to 200 x 200 or less.
Click Apply .
Scroll to the bottom of the page and either click Save a copy or Replace original.
Open your User Conrtol Panel, select Edit avatar in the Profile section, then paste the Direct link (not the IMG code) of the resized image into the Link off-site box, then click Submit and if it has been done it correctly, the image should show as your avatar.
[Edit] If the photo was uploaded to Photobucket as a reasonably high resolution image, then it may still be over the 6KiB maximum file size?
