applying texture to custom plane geometry in Threejs

Hope this helps Can it be because you texture gets scaled down(so it can be repeated 100 times on the surface) and you just can't see the details of it? If the texture is dark itself this could be the matter. Maybe you try it with floorTexture.repeat.set(1, 1); to see if it actually gets applied.
Also you may consider to include your texture, so that anyone can test against it. I just ran your code in r.58 with a custom texture and it worked fine for me.

I think the issue was by ths following , You can create a texture with drawing on a canvas or draw a texture you want in any image editor, then apply it to a sprite. If you want the sprite to have the same size, independent on distance, then look this answer. Both my answers have jsfiddle examples.

wish helps you First of all, you need to add enable shadowMap on Renderer. In your example, you assign shadowMap property as 'true' which is wrong.

renderer.shadowMap.enabled = true;

floor.rotation.x += Math.PI/2;

floor.rotation.x -= Math.PI/2;

light.shadow.mapSize.width = 2048;
light.shadow.mapSize.height = 2048;

fixed the issue. Will look into that further A single vertex can't have more than one texture coordinate. Since each vertex in a cube appears in a corner and is part of three different faces, you'll need to repeat the vertex data three times and match that up with the texture coordinates and then reference those with your indices.
Another way to look at it is that the same index that you're using to reference the vertex is also used to reference a texture coordinate, so since you only have 8 vertices, you'll only be able to reference the first 8 texture coordinates.

// Indices that turn the source data into triangles
// ------------------------------------------------

int indices[] = {
    // bottom
    0, 2, 1,
    1, 2, 3,
    // back
    10, 14, 11,  // 2, 6, 3,   + 8
    11, 14, 15,  // 3, 6, 7,   + 8
    // left
    16, 20, 18,  // 0, 4, 2,   + 16
    18, 20, 22,  // 2, 4, 6,   + 16
    // right
    17, 19, 21,  // 1, 3, 5,   + 16
    19, 23, 21,  // 3, 7, 5,   + 16
    // front
    8,  9, 12,  // 0, 1, 4,   + 8
    9, 13, 12,  // 1, 5, 4,   + 8
    // top
    4, 5, 6,
    5, 7, 6
};

// Custom geometry data for a cube
// -------------------------------

SCNVector3 vertices[] = {
    SCNVector3Make(-halfSide, -halfSide,  halfSide),
    SCNVector3Make( halfSide, -halfSide,  halfSide),
    SCNVector3Make(-halfSide, -halfSide, -halfSide),
    SCNVector3Make( halfSide, -halfSide, -halfSide),
    SCNVector3Make(-halfSide,  halfSide,  halfSide),
    SCNVector3Make( halfSide,  halfSide,  halfSide),
    SCNVector3Make(-halfSide,  halfSide, -halfSide),
    SCNVector3Make( halfSide,  halfSide, -halfSide),

    // repeat exactly the same
    SCNVector3Make(-halfSide, -halfSide,  halfSide),
    SCNVector3Make( halfSide, -halfSide,  halfSide),
    SCNVector3Make(-halfSide, -halfSide, -halfSide),
    SCNVector3Make( halfSide, -halfSide, -halfSide),
    SCNVector3Make(-halfSide,  halfSide,  halfSide),
    SCNVector3Make( halfSide,  halfSide,  halfSide),
    SCNVector3Make(-halfSide,  halfSide, -halfSide),
    SCNVector3Make( halfSide,  halfSide, -halfSide),

    // repeat exactly the same
    SCNVector3Make(-halfSide, -halfSide,  halfSide),
    SCNVector3Make( halfSide, -halfSide,  halfSide),
    SCNVector3Make(-halfSide, -halfSide, -halfSide),
    SCNVector3Make( halfSide, -halfSide, -halfSide),
    SCNVector3Make(-halfSide,  halfSide,  halfSide),
    SCNVector3Make( halfSide,  halfSide,  halfSide),
    SCNVector3Make(-halfSide,  halfSide, -halfSide),
    SCNVector3Make( halfSide,  halfSide, -halfSide)
};

SCNVector3 normals[] = {
    // up and down
    SCNVector3Make( 0, -1, 0),
    SCNVector3Make( 0, -1, 0),
    SCNVector3Make( 0, -1, 0),
    SCNVector3Make( 0, -1, 0),

    SCNVector3Make( 0, 1, 0),
    SCNVector3Make( 0, 1, 0),
    SCNVector3Make( 0, 1, 0),
    SCNVector3Make( 0, 1, 0),

    // back and front
    SCNVector3Make( 0, 0,  1),
    SCNVector3Make( 0, 0,  1),
    SCNVector3Make( 0, 0, -1),
    SCNVector3Make( 0, 0, -1),

    SCNVector3Make( 0, 0, 1),
    SCNVector3Make( 0, 0, 1),
    SCNVector3Make( 0, 0, -1),
    SCNVector3Make( 0, 0, -1),

    // left and right
    SCNVector3Make(-1, 0, 0),
    SCNVector3Make( 1, 0, 0),
    SCNVector3Make(-1, 0, 0),
    SCNVector3Make( 1, 0, 0),

    SCNVector3Make(-1, 0, 0),
    SCNVector3Make( 1, 0, 0),
    SCNVector3Make(-1, 0, 0),
    SCNVector3Make( 1, 0, 0),
};

CGPoint UVs[] = {
    CGPointMake(0, 0), // bottom
    CGPointMake(1, 0), // bottom
    CGPointMake(0, 1), // bottom
    CGPointMake(1, 1), // bottom

    CGPointMake(0, 1), // top
    CGPointMake(1, 1), // top
    CGPointMake(0, 0), // top
    CGPointMake(1, 0), // top

    CGPointMake(0, 1), // front
    CGPointMake(1, 1), // front
    CGPointMake(1, 1), // back
    CGPointMake(0, 1), // back

    CGPointMake(0, 0), // front
    CGPointMake(1, 0), // front
    CGPointMake(1, 0), // back
    CGPointMake(0, 0), // back

    CGPointMake(1, 1), // left
    CGPointMake(0, 1), // right
    CGPointMake(0, 1), // left
    CGPointMake(1, 1), // right

    CGPointMake(1, 0), // left
    CGPointMake(0, 0), // right
    CGPointMake(0, 0), // left
    CGPointMake(1, 0), // right
};

hop of those help? A CircleGeometry is similar to PlaneGeometry always flat. Their vertices are generated in the XY plane without depth. Meaning the z-component of all vertices is 0.
If you need a geometry with a volume, I suggest you use CylinderGeometry or BoxGeometry instead.