It uses stamps from Artistic Outpost, in this case the 'Serenity' plate:
lots of stencilling, some PaperArtsy Fresco Finish London Night tinted Grunge Paste for the tree which I then coloured with pencils to give a 'barky' look (or should that be 'barking'!!!):
You can get Artistic Outpost stamps from That's Crafty here in the UK. They've got a great range of images and are well worth the money.
Thanks for looking!