There's nothing wrong with principally using studio artwork, but I think you should stylize your additions to make things more seamless. It's very easy to see where you have added your text, features box, etc... because of the difference in quality and style.
First off, you're missing apostrophes in a couple of places. (It's Daylight Robbery and Don't wait for the lift.) And in the line, "follow the rooftops for 2 miles" it looks like the word "for" is inadvertantly bolded.
On the phrase, "How DO they get away with it?" it looks like the line underneath DO is part of the original image but the rest was typed in. It's just little stuff like this that gives it away. You should redraw the line and then apply a very slight blur to all of your text. It just looks too clean compared to the images.
The special features box also looks a bit out of place. You should continue the theme and place one of those thumbtacks on it and give it the drop shadow. Maybe try to give it that watercolor look of the images. Also there is very noticable aliasing on the edges from where you have angled and distorted the lines. It's unavoidable. So you should use your blur tool with a light setting and trace the edges to manually anti-alias it.