Yes, photoblog do earn you credits.For bagging good credits
1. You should post High Quality Pics.
2. The pics should have some content.
3. The pics should be logical to the title.
4. The pics should be clicked by you or you if you are copying from somewhere mention the proper credits .
Yes. You'd earn around 40 - 60 credits for a photo blog. Then again your work quality determines the number of credits. Put up HD quality pictures and write a caption/detail about them. Tag the location and put up a eye catching Title.