Irrlicht Engine

Try changing the rendering, Software tends to lag, try OpenGL or DirectX

Atmel ARM Micro's are my speciality, but chances are they bight barf...
unless you want to create a whole new irrlicht libary for Assembler or Crossworks... but would not be worth the effort...

Although they look really nasty, You could go for a Doom look and make them from Billboards

I reckon more Rendering Device Support...
and probally a simple event handling method like int GetKey();
And also a bit more GUI options and Primatives...

it needs Built in Reflection, Portal, Refraction and Rain scene nodes...