Concept Art

Animation tests for the hanging mummies, as well as "Moth Mummy-chan" (みのむしミイラさん) on the right.

Stone 職人による手彫りのSの文字が石の1つ1つに丹念に入れられた原始回帰的武器。

Stone A primitive weapon that has the letter "S" carefully carved into it by a hardworking craftsman.

メタルスラッグ タイプR 外観は通常のメタスラと同じ（色ちがい） ボディの素材とサスペンション・エンジンなどが違うらしいゾ。

Metal Slug TYPE-R The appearance is the same as the ordinary Metal Slug (colour variant) The body's materials and suspension engine appear to be different.

A run-down of the Type-R. The labels point to the suspension system, engine and chassis material, with a 160cm tall Eri for reference. (she's actually 168 cm, but let's not split hairs)

A bizarre collage from the Metal Slug X art gallery, chucking a whole pile of sprites and backdrops around the place - including a bunch from Metal Slug 3! X's PlayStation port was released ten months after 3 came out in arcades, but it's still an oddity.
There's the Drill Slug, the Rebel Armor, Elephant Slug, Ostrich Slug, Slug Copter, and the giant falling soldier from the first Metal Slug for good measure.

Enomosiki says: I'm guessing that this is Meeher, one of the planners for the Metal Slug games when SNK was still around. At least he's not mooning the viewers.

An unfinished poster only seen in the art gallery. The baby and alien abduction suggest it's X, but then there's an elephant in centre frame. You're not in this game, buddy!

Concept art is sourced from the Metal Slug X PlayStation Art Gallery, Neo Geo Freak July 1999 (thanks to Divison 六 for the scans!), the Metal Slug 6 Art Gallery, the Metal Slug 10th Anniversary website and the Metal Slug Attack Illustration Gallery.