I think the answer is making a new geometry,set your own vertices,faces that meet your demand and then set the faceVertexUvs and materialIndex to make it well textured.
vertices.forEach(function(v){
geom.vertices.push(new THREE.Vector3(v[0],v[1],v[2]));});
faces.forEach(function(v){
geom.faces.push( new THREE.Face3( v[0],v[1],v[2] ) );});
I have a example here:multipleTexture
Also note that
using textures whose sides are a power of two is ideal-
webgl texture
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