I mean does it have a browser where you can view the subfolders of data8 and look at thumbs of the .d files containing images?
By default - no, it doesn't.
When you have image opened in IrfanView, you can go to the next image in the folder with [Space] button and go back to the previous image with [Backspace] button on your keyboard.
.d files are not image files so IrfanView don't support those files by deafult. But this can be changed.
Go to
Options > Properties/Settings (or simply hit P on your keyboard), and select
Extensions (screenshot). Add "D" to the list of supported extensions (marked with red color on the attached image) and click OK. Now you can browse the .d files with [Space] and [Backspace] button on your keyboard.