One question, one thought ...
Question: You posted two images, one in red and black, and the other in purple and black. The red/black image looks like it is of lower quality (eg, lots of jpg artifacts). The purple/black image appears to be a photo of a framed poster. From the info you provided, I can't figure out if you want us to select which we prefer, what the relationship is between the two (eg, was the red one a work-in-progress image, while the purple one was what you actually had printed?, etc.).
Thought: Although this may have been your intent, and is part of the style you are emulating, but for the purple one, my personal preference would have been to surround the poster with either a thin key line, or make the color of the surrounding area something other than black to prevent the colors and shapes of the poster (i.e., the black of the upper thought bubble) from "bleeding" into what amounts to a simulated mat area.
Letting the black of the poster continue unimpeded right into the black of the surround does have the interesting visual effect of separating the upper and lower purple areas, and, in a way, simplifies what we are looking at (and this probably was your intention as well as a more "realistic" style emulation and way to display the poster), but when I personally weigh the pros and cons of it, I would still go with a way to make clear where your work "stops" and the surround (aka, mat) "begins", but I'm very literal, LOL.
Cheers,
Tom M
PS - Maybe a double-mat design would accomplish both goals,i.e., a thick black inner mat and a narrower, outer mat of different color / texture to set off the entirety of the poster (your work) from the method of displaying it.