The short answer is I'm lazy T-T but i will take your frame advice into account. That's the first time I tried so I really didn't know what I as doing. I will try and add a frame to my next project and see how it goes.I'm a Little Monster is a bit uninspired. Not much going on there. Even if you were going for something quick and simple, perhaps a bit more could have happened here. At least something going on in the background. The frame might even make it look incomplete. Sometimes when you add an element like a frame, it will look kinda unfinished. Frames should be carefully considered as part of the composition and not just thrown down without much consideration. I see that you tried to do something with it, but why exactly is it there? What does it add to the composition, besides just being there? A frame contains or excludes design elements in a piece, but in this case it's not really doing much of either.
Your Retro piece is a better use of the frames. They aren't distracting and are a design element to help give the piece structure. It doesn't clash with the images at all, and the use of them both have a purpose-- they help create depth by being layered around the render instead of just existing on top of it. I've also seen the text version of this one, and I like the text version more. The bare version just feels like something is missing.
With the text retro piece I was just unsure if I could post it. A weird anxiety thing, but! I am glad I made it. Did you like the placement of the text?