The Woman and Bird in the Night: Can you solve the riddle related to this painting?

At my school we have this thing called the breakout box and there's a challenge. It's pretty hard, so me and some of my friends have been working on it. The idea is that there is a box with a bunch of locks on it and clues around the room to help unlock it. You have to use the clues to get the locks' codes - a 4 digit number - and open the box. So far we've opened every single lock except one. We've researched for about two days and we can't figure this out, so I decided that I would ask the online community.

The riddle is on the wall. There is this painting and we found out the painting is called 'The Woman and Bird in the Night'. It's by Joan Miro. (see below) The teacher who made the riddles wrote 'e=16' in the bottom corner on the white part of the paper. We aren't sure if this is a hint, a key, or something to throw you off. We really need help with this because we have unlocked all the locks except one. This is the only clue left, and the answer must be a 4-digit combination.

I'll be checking for answers about every hour.

Here is the picture:

Here is a link to a larger version of the painting if anyone needs it.

It might seem like this has many answers, but there is only one answer and it is a four digit combo that uses numbers. I do have access to the lock and every day I have been going down and checking all the combos that people have thought might be a possible answer and then adding a comment letting people know if anyone was right.

Here is a pic of the picture on the wall:

• @Conner, welcome to Puzzling SE. The community is much more likely to help you and will be able to help you much more easily is you were to take a little time working on the formatting and punctuation of your question. Jan 27, 2016 at 20:16
• Thanks for reviewing it looks good if anyone is wondering why my spelling is bad it's because i have dislexia Jan 27, 2016 at 21:06
• @conner, what are the previous lock's combinations? could you give us a list? how many locks were there in total? Jan 28, 2016 at 11:28
• Observation: There are 8 pairs of black circles connected together in the painting. In other words, 16 black circles. "e=16" might be hinting that this is relevant somehow? By the way, could something that teacher taught your class be relevant here? Also it might be helpful if you briefed us on some of the other puzzles you solved to open the other locks. I know you already said that you thought they weren't relevant but you can't be sure until after you've solved this one. :P Jan 28, 2016 at 13:35
• Can you show us a picture of where he wrote "e=16"? It may not actually be "e=16", it may be intended to be looked at another way which could be another clue. Jan 28, 2016 at 20:52