Original description from derpi:  
Speaking of rom hacks with potential… Four colors of yoshi means that Spike can ride on Twi, Rainbow, Applejack and maybe Pinkie Pie. Yoshi wing sprites default to blue.
 
When Spike collects coins, his immortality increases every 100 coins.
 
Mushroom is replaced by the Greedy Gem. It’s so valuable, spike grows in size and becomes stronger.
 
Fireflower is replaced by the Fire Gem. It’s value increases spike’s dragon powers so he can shoot fireballs!
 
Feather is replaced by the Winged Gem. It’s value increases spike’s dragon power so that he has wings and can fly!
 
Star is replaced by the Shining Gem. It’s value is so immense, that Spike is unstoppable!
 
P-Switch is replaced by the Dragon’s Eye. It turns blocks into money! More moneyyy!
 
Silver P Switch is replaced by the Silver Dragon’s Eye. It’s even more powerful, and turns enemies into coins! so much money!
 

 
other ideas - Fortresses are replaced by cave levels, and renzor are replaced with Diamond Dogs throwing gems.
 
But, I know SMW hacks can go wild places so, that could even be different.
 
(also, I’m on a computer with only MSPaint)