Here's the list of collectibles in Episode 1:
1 - Deer Skull - Act 1
2 - Plastic Flowers - Act 1
3 - Real Flowers - Act 1
4 - AJ’s Drawing - Act 1
5 - Cat Skull - Act 2 (CAN BE FOUND ON BOTH PATHS)
6 - Tenn’s Drawing - Act 2
Here's where you can get each one:
1. Deer skull - Can be found at the train station when you first arrive there at the start of Episode 1. Located outside past the tire swing then turn right and it'll be on top of a few things.
2. Plastic Flowers - Before going towards the music when going to find AJ, go behind the stairs (to the right side), there you'll find the flowers on a small table.
3. Real Flowers - When given the task to "Help AJ make friends", go right towards the dorms then turn left and walk forwards and you'll find the flowers on a bench.
4. AJ's Drawing - No matter if you choose to keep or give the box to Violet, she'll let AJ finish the drawing, the only thing that changes is how Tenn will feel (he says something about it at the start of Act 2 in Marlon's office)
5. Cat Skull - I've seen many people say that you can only find this on the fishing path but nope. You can find it on both paths. On the fishing path, the skull is located on the fireplace. And on the hunting path, the skull is located in the grass near Aasim.
6. Tenn's Drawing - When Tenn asks if he can draw you in the picture, you NEED to pick "Sure, draw me in" and he'll give you the drawing.