Hi Marcus,
This is not a bug but a new feature! As you know it, the localization is a major feature of dnn. Previously, it was not possible to have localized graphics buttons. Now, you can!
In my post you can read:
At last, a dratf of the new Templating Guide is available for web designers!
In the chapter 3 of this guide, you can read:
All texts used with labels and links generated by tokens are defined in the resource file ProductDetail.ascx. To facilitate the translation, the names of image buttons are also defined in this resource file (like addtocartimg_{0}.gif in AddToCartImg.Text) and the current language code (e.g.: en-US, fr-FR, ...) is added to the end, to build the full file name (addtocartimg_en-US.gif). You have to create your local version of image buttons to translate the Store module into a defined language. A Photoshop model (buttons.psd) is provided in the folder Images to help you create your own localized buttons.
Moreover, Benoît (my Co-Lead) have bloged about the new features two month ago!
It's always the same story with users. When they do not have documantation, they cry and complain. When I use my 3 weeks of holidays to write a full doc about templating, they do not read it.... and complain! ;-) It's not fair! The next time, I will stay on the beach instead to be in front of my computer.
Concerning the "AddToCart_blue_2" button, I'm sorry but I loosed the psd file after a crash disk several month ago! Then, I can't help you on this. But you can found a lot of button models on the Internet for free. Search for "button psd" with Google.
Gilles