The design is clean, and the overall aesthetic fits the theme of the postcards. The images selected are professional and the solid background makes the text very legible. The design is consistent in all three compositions, and it seems very doable, not overly complex. For the mobile-sized designs, I feel like the font is a little too thick which makes the entire composition slightly top heavy. Maybe try to play with some lighter weight fonts. Also, when the screen gets narrower, the text would cover the person's face. One suggestion that I have would be to make the text change colors when the screen size gets to a certain point.
In addition, some of the images are pixelated. Also be careful when you crop the images. Some of the edges are not super clean. But overall, it was very well-designed.