For this, you don't need any tool except for LNZPro, preferably version 3.2 or later.
You can download it from my "Nicholas' Tools" pages.
First, let's change the Adoption Centre bitmap. You don't need to, but hey, it's nice to have your own breed's picture, isn't it! So, open the breedfile into LNZPro. Click on the cross beside BMP and then put your cursor on the name of the cat or dog -- in this example, it's POUNCER. Choose "Replace from file" from the Edit menu.
Navigate via the dialog box that opens, until you find where you put the bitmap you want to use.
Then hit the Finish button.
Your breed is now non-overwriting. Yay! I told you it was ultra-easy :-D
If you want to do the ID number and name a bit differently, click here
If you want to make it have different 2-letter mnemonics and a different AC name, go on to