As for the image you created, I agree with both posters' critiques.
The volcano flame should curl around more as it does on the original and be softer and lick out more as Sam points out. And as you have agreed, besmirched makes a good point about the flames. Very important that you have variation in the elements. Yeah, it takes a bit more work, but all you need are a few flame brushes, layering size and color to add those flourishes. Of course, you can always just copy more flames, but for me it is more of a challenge to try to recreate reality with brushes. To each his favorite own method.
The extraction of the boy figure is in need of work (as Sam said) and oddly, his color balance seems off from the other greys surrounding him. He also seems too large in proportion, though I suppose the size of a lava flow is indeterminate.
Besmirched made comments about the angle of the flame from the volcano. One suggestion I have to reshape the middle and give it more fullness and perspective is to use transform>warp and pull the middle grid forward. Transform can be a lot of fun to play with. Just be careful how much you bend the pixels. They will deform.
But . . .
the idea is very creative and the composition is great. I like it.
Now, as you make note, the images you are using to compile your manipulation are small and low res. Do try to get all your images in large size or high resolution, and post them here in large format so we can enlarge them and really appreciate the work you've done. It also allows us to zoom into areas that may need greater critique/advice.
And finally, we prefer that all images from another artist/photographer that you use be credited and conform to any copyright or usage desire of that artist. If you need guidance on how to make those determinations, just ask us. We've been there/done that. It's also kosher to post those originals and again, gives us a better idea of the scope of the work you did.
So, keep it up. Move on to the next idea and show it off! Don't call yourself lazy, just challenge yourself, and above all, have fun moving forward. So much to discover.