[JerryMaffz]

The thing to do is set up an account for your tortoises only, mine is called JerryMaffz, and only add tortoise pictures as a free flickr account has public access.
Upload in the same way you would in photobucket, then go to the photo you want to share.
At the bottom right of the image is a curved arrow icon, you need to click that.
Choose the BBCode and copy the link. (you can choose size on the dropdown, I use Medium)

Paste to the post you are making but (now the tricky bit) .
The only bit of the code you need is everything up to, and including [/url]...Everything after this generates flickr icons etc and can be deleted.

Sounds much more complicated than actually doing it.