Ok this is my very first time of writing a critique so I will really try my best xD
I know this is unfinished but looking at the detail you have made so far I can really see that this picture will turn out into something epic I adore the detail you did on the eyes <3 the blue colour.. it looks so prettyyyy You always give that nice style on the eyes making it both realistic and cartoon-ish.. it's so good ^^ What seems to bother me a biiiit though is that they look like they are popping out a bit too much at the part where they are connecting with the muzzle.. maybe it's just me xD
From the way you shaded his muzzle I can also understand where the light is coming from which is something that many people don't do on their Sonic pictures xD but I'm glad you did You should shade the rest of the character the same way (I know you will )

I'm looking at it and really wonder how it will look when it's done xD You are very good at using the open canvas program I hope that you will finish it soon!