I'm no expert when it comes to finding unused stuff in games -especially Genesis ones -but here is a bunch of stuff that goes unused in El Viento:

Unused sprites


Unused text that is much more plain than what gets used. My palette is wrong and I don't know what the correct one is, but I'm guessing it'd be white.

These building sprites are loaded when the fourth level starts, but are never seen during gameplay. An early screenshot of this level shown in the August 1991 issue of Beep! Mega Drive does feature a screenshot showing what look like these sprites in the background, but they ended up being removed for the final game.

What appear to be even smaller building sprites. Like the ones above, these are loaded during level four's opening, but are never used anywhere.

A couple of sprites loaded during the final boss battle, but aren't used for anything. These look like they could have gone on the larger pillars seem in the room.

Some more sprites that are loaded during the final boss, but don't get used. I'm not sure what these were meant to be for. Early floor sprites, perhaps?

Unused music

The following two tracks can be heard in the game's sound test, but aren't used anywhere in the game itself:

Unused track #1
Unused track #2

The first track is number 8 in the sound test, the second track is number 21. I've got no idea where the first track could have been used in the game. My theory for the second track is that it was meant to be played for when Annet obtains a new magic spell.

Unused intro text

Found by Ragey, the text below is for the game's intro. Strangely this English text is only in the Japanese version. It features several typos that I've left unchanged below, and the intro text for the English version of the game would be re-written. Even stranger is that a prototype version of the game, seen as the 1991 Tokyo Toy Show, featured this early text in it -even though it was on display at a Japanese show.

Final version
The wind is descending.... it lifts its great arohing neck in order to shape the evil world of the future
"Tornado" is approaching........ With its huge funnel upright, in order to create a dreadful world.
Now the power of the great wind El Viento has began to format
The powerful tornado "El Viento" has just started it's activities.
New York, 1928
the skyscrapers are being coverd with the dark power of demons
In 1928, in New York, the sky scrapers are about to be overwhelmed by the force of an evil, dark world power.
The fanatics who beleave in the otherworldly demon Hastur are planning a ceremony to beckon him
The fanatic believers who worship the devilish lord from the outer world, Hastur, are planning a ceremony summoning their lord.
Henry, the founder of organization, recalls Hastur and plans the destruction of mankind
The founder of the religion, Henry, is plotting the destruction of mankind by summoning of Hastur.
The young girl Restiana, has inherited Hastur`s powers
Restiana, a young woman who was given power by Hastur.
Along with the religious group Al Capone, the mafia strongman is engaging in secret maneuvers to recall Hastur
Vincente DeMarco, kingpin of the Mafia group, pulls strings in a conspiracy with the religious group for the summoning of Hastur.
Demon destecond to the Empire State Building, the magical skyscraper
An evil lord is descending on the Empire State Building, a towering structure, the landmark in New York.
A young girl is running now in order to crush evil ambitions
A young girl comes to smash their terrible ambition.
The young girl Annette is pitted against the cursed blood of Hastur as well as the religious group
Annet is destined to confront the religious group despite her accursed blood relation with Hastur.
Why are you making trouble for us, Annette?
Aren`t you one of us, drawing on the blood of the Lord Hastur
"Why do you stand in our way, Annet?"
"Aren't we of the same blood as Lord Hastur? You are supposed to be on our side."
I`m a human being just like you!
"Because you and I are human beings."
It all takes place in New York
The life and death struggle has begun!
Fierce battles have just begun in this evil-infested New York.

Unused level

An unused test level, which is extremely hard and features several sprites not seen anywhere in the game itself. As the test level is so large I've done a separate page about it here.