There is no limit to the number of pictures in your post. However, the credits earned are based on quality of the content rather than the number of pictures. So, avoid posting any random pictures just for the sake of increasing the count.
You can upload as many as you want . But photos have to be of very good quality and you need to write some description about the pics so that it is a value add to the reader. you won't get any credit for just uploading the pics