Depends on what you do with the pictures.
If you jerk off everytime you look at the pictures, then it's porn.
But if you, like you said, look at the pictures and get motivated to go out and sarge and / or work on yourself.. and don't touch yourself each and every time you look at them. Then I'd say it's a motivational collection.
Though I would really suggest to hide the folder somewhere safe when you get some friends and/or HB's over to your appartment. Chance is they will sit behind your pc, and then open the folder 'motivation'. It's pretty rare that someone has a 'motivation' folder on their desktop, so people will feel the urge to open it (at least, I would). And if they see the pictures.. well.. you know what'll happen then.
cheers