1) Think about the intention behind using all lowercase (even for "I") - gives a certain feel
2) For the first postcard I'm not sure if I like it being a sentence fragment rather than a complete sentence
3) Each post card has a different color system - first is all color, second is grayscale with a one color highlight, third is all grayscale
4) The weight of the type is definitely hard to read - more so at the mobile size than the desktop size
5) Think about the cropping on the mobile mockup for the first image - maybe push it to the left so that the text can still be to the right of the legs (so it doesn't have to move too much when you shrink the screen)