What specific types of textures did you have in mind? Do you want wooshes, chimes, rhythmic echoes? Perhaps something more harsh?
A Yamaha Magistomp is replete with atmospheric noise potential and has a fairly small footprint for what it is capable of doing ... but the PC editing interface can be a real pain.
I can make additional suggestions once you provide me with a better sense of the sounds you are looking to make ... and there is also a great ambient equipment guide one of the specialty sections of this forum.
