@lucy_gow First off I like the concept, and the colors help draw your eye to where it needs to go.
So just 2 simple things that stick out to me, first are the paws of the tiger. I'd say find some reference as they seem to be the weaker part of the drawing here. Also, if they are supposed to be pushed against the glass we could probably see some of the padding on the bottom of the paw
Secondly, the tiger is getting larger as it goes back which makes it look a little fat or just a little strange. Usually you think of tigers being more sleek so I'd taper the back of the tiger as well.
Overall a great start!