Obviously, any sort of analysis of a piece of artwork is incredibly subjective, and you will see a wide variety of differing opinions on any individual piece, but here are a couple things I think I see at work here. First of all, it looks like Jack is leading the eye from the top of the page down to the main characters using the flashing planets that are eclipsing a supernova at the top of the page. The red line below not only shows how a reader might look at this page for the first time, but it also shows the Surfer & Ardina’s path to freedom.
These two circles at the center-top of the image (surrounded by more circular bursts around them) are in the far background. Looking at the whole page from top to bottom, the eye naturally pulls back from background to foreground, over Galactus‘ shoulders to the Surfer and Ardina behind him in the near foreground.
The eye is led from the cosmic spectacle taking place billions of miles in the background, to the drama taking directly place behind Galactus. Also notice how Galactus‘ stance symbolizes stability and serves as a contrast to the flowing action around him. Galactus is also an obstacle between the Surfer/Ardina and freedom outside of the space craft.
Another interesting aspect of this page (whether it was meant as an interior splash or possibly an advertisement or back cover) is the fact that Jack had to leave room for Stan Lee to add captions and text to his artwork.
With black circles, I marked off three probable locations for either a caption or a word balloon. It’s interesting to see that Jack still filled in the entire page with detailed artwork because he had no idea where Lee would add text, and Jack wanted to make sure the image is complete and easy to ink. Also, look how well-balanced the image is with the addition of the balloons, showing that Jack constructed this image to be dramatic and dynamic, regardless of how much text Lee decided to include.