Oh em gee Shannon, I love this concept so much!!! Lol~~ I thumbnailed some concepts just to explore some ideas and I'll share them here with you!
Top left is basically your sketch except I also included the street as Dima suggested so that you can better see the scale with cars/people/etc. I also wanted to add more depth by adding a building super close to the viewer on the right side and then some fun shapes like telephone lines on the left and some birds flying through the scene to give that extra lovey mood :). The blob on the bottom left corner is... I don't know, haha. I just wanted to add more depth to that side, too. Maybe it could be a portion of another building, lol.
Top middle is a view from inside a building with people looking outside a huge office window watching the two godzillas meet each other. But it kind of looks movie-theater-esque, and I don't know if you want that feel.
Top right is a shot closer to the ground, but I don't like this one because the POV is at a weird height. Not exactly ground level, not aerial, somewhere strangely in between, haha. Since we can't see the full Godzilla on the left, I gave her a skirt to signify that she's a girl, lol. Just... ignore this thumbnail, haha.
Bottom left is a night scene at ground level so we can really see the scale of the two godzillas with the buildings around them and the moon above. I drew "through" the frame so I can make sure I get proportions looking right, but I kind of like the way it looks with the legs coming out of the frame, but that's a judgment you can make once you get your composition down.
Thank you so much for sharing your process with us and letting us critique your work! I had so much fun making these thumbnails, haha! And composition is something I'm trying to improve on as well, so I really appreciate the opportunity to practice! Can't wait to see how your final art piece turns out!