This is so incredibly beautiful and poignant! I love the monotone colour palette you've used for this, it makes the picture feel so quiet and peaceful. Snape still frowning, even in sleep = fantastic. And I love how you can see his shape, even underneath the sheets.
And Harry, oh lord. I love his long, gangly, youthful limbs and yet his frame is still so small and skinny. Amazing job with overlaying photoshop colour on pencils; I've been trying to do this myself in some non-fandomy art, and it's definitely not as easy as it seems/looks. *admires muchly!*