Not sure of the size limit, there used to be information about this but I can't find it. I typically downsize to 800 x 600 pixels, 75% quality, and that works well. Size is usually under 100 kb.
Hi! Welcome to Basenji Forums!
Do you have any photos of Tucker? It would be great if you can post them in the Show Off Your Dog thread.
Let us know if you need help posting your photos.