Most of these images were from IGN.
There’s nothing wrong with this image, other than the alphabet being shown instead of the standard text. I presume that was for code testing purposes.
Early Footage
The old screenshot features a really crappy looking Gimlet and a tank that appears to only have three shades, unlike the superior final version and it's five shade tank.
And again, Gimlet is ugly. The explosion is also a tad different, and there’s a dark outline surrounding the island in the background.
The background is horrible white in the prerelease, but black in the final, and just like the second image, the boss seems to lack detail.
Red Eye’s jetpack appears to be green and red, whilst her jetpack in the final is green and blue.
Margaret doesn’t speak like she’s using AOL in the final. Plus, there appear to be some minor differences on her design from the final, such as the eyes and nose being slightly higher, and repositioned hair.
More of the same jibberish text.
Same problems as the fourth image: White background and less detailed boss. I’m also not too sure if you can get a tank to this battle, but that may just be my bad memory.
This level isn’t anywhere to be found in the final, nor do you see that background anywhere either. Plus, I think the sprites may be different here. Note the Heavy Machine gun icon, despite being in the Slug Mariner.
This is the same as the final, except for all the prisoners being named “METALSLUG”.
This is also the same as the final, except for the fact that green soldiers never appear in that area, only tan bazooka troops; and they don’t jump around and shoot at you, they merely stay in the corner and attack you from there.
And that Heavy Machine gun icon shouldn’t be there, and I presume they’re cheating, with the full ammunition for both the gun and bombs.
Other than the severe colour change that all images from the official Metal Slug: 2nd Mission site suffer, the differences are the option entries (like Easy, A, and such) use the same font as the options themselves, and key type A is actually the final's key type B.
If what I think is true, and this is from the first mission, then the only difference is that no explosive mines appear at that point in the area. Explosive mines only appear when the trees in the background are centred. The rest are just harmless buoys that sink.
The foreground is the same, the signpost thing that passes by is the same, and those enemies are there in the final; I just killed them to make it easier to take a screenshot. However, the background is much more simplified in the image. There are only those massive girders, there aren't any clouds, wires between the girders, or any of those towers near the bottom.
The prisoner was changed from being tied to a pole to just plain tied up. The clouds also look vague in the image, and the binoculars-wielding soldier was either killed before the image was taken, or he wasn't there.
Same colour changes. However, Gurraka (008, Mission 02) was once known as Garrick; I've no idea why they would translate the name to English only to make it a Romanisation again.
The screen has become speckled, and the font used is ever so slightly different. It's outlined in brown, but has no outline in the final.
The seaweed is red in the prerelease, but green in the final. The gradient sky is also slightly different.
Apparently, Gimlet's jetpack was part of his upper body sprite, as it shares his orange and white colour scheme. In the final, it's blue and violet.
