olguy162 : I'm just going to go ahead and give my pennies worth.
Note : I know nothing about Terraria, so I as good as useless where that is concerned. :s

First though... Here is some advice.

The most important thing is to make sure you're doing it for your own satisfaction,
not tailoring it to the taste of others just to appease them. (though it is a balance between the two)

Don't strain yourself for inspiration either, that's the worst thing you can do! When you try and force things forward it can do more damage then simply being relaxed towards development, (attitude, I think, is very important for the quality of your work)
and do it at your own pace.

Idea :
Here's a throw-away example of some scenarios/concepts you can mess about with the Mario resource's.
I didn't make this for entertainment- just for an example. So its not that funny...
(I'm assuming here that your aiming for a humorous parody of Mario/Terraria)

Scenario Title : Marios Nightmare.

Mario is deep within Bowsers castle, standing before the final gauntlet between him and the captive (and captivating) Princess Peach.

Browser secretly watches Mario from his control room...
Gloating to him-self that this "final gauntlet" is the most ingenious he has ever designed...

Full of lava pits, crushing walls, tight-ropes, collapsing floors, and swinging bladed pendulum thingies...
Bowser : "And now what are you going to do? HAHAHHA-" Bowser stops mid-laugh as Mario effortlessly makes it to other side...
Bowser : "What is this? I don't even-"

With a deafening roar Bowser stomped out the control room to confront Mario for a "final showdown" ...
With an over-the-top dramatic entrance, Browser jumps down before the final door, ready to give everything he has got against possibly the most meddling plumber in history...
"?"
No one was there... Bowser waited and waited but to no avail : "I've been stood up! Why that little good for nothing-" something red caught Bowsers eye... A hat, Mario's red hat! Right at the edge of the arena! Bowser peeked over the edge...
Nothing but a sheer drop to a high-speed dive into hot death... "Oh my god!" *here you might think of a sentimental speech for browser to give about Mario-and how he didn't deserve to die*  Bowser : "He was just a d*mn good plumber d*mnit! WHY?!"

Wiping a tear from his eye he looked back down into the river of lava- taking the moment to quietly reflect on all the years of pointless battle *here he could say that he will amend his ways- to become a better person- maybe go into the theme park business*

He picks up Marios hat to throw into the lava- *THUNK!*
Bowser stiffens, going cross eyed. Bowser : "Argh..." Mario had snuck up on him- and hit him with a lead pipe (he is a plumber after all)*

Mario slowly reached past Bowsers back and pried the hat loose form Bowsers hands... *I'm running out of time here.. Mario then pushes the stunned Bowser over the edge* Mario : "Its'a dirty job, but some body's got to do it." Mario said while replacing his hat..

*the dream ends when he finally frees Peach- he is expecting the obligatory kiss...But when she turns round shes a Bowser-like thing*
Peach : "Thank you ever so much for rescuing me..." *Kissing noise*
Mario is paralyzed with shock. And then he wakes up...
Mario : "MAAHHMAAHH MIAAAck!" *Voice cracks*

Last one for now- I really am running out of time here...
Peach, after all the years of capture etc... Someone thinks its a good idea to get her to learn martial arts.(to the displeasure to everyone, except Peach) Have fun with that one...

Sorry out of time... And too tired to continue- I hope this helps.
Note : Didnt get a single vizz for this... So dont judge me...