How create tool palette from a existing dwg file? so that we can use this layers to new file easily... 

Is this custom tool palette located on a server or on another workstation?

As we able to create a palette from existing block by dragging into toolbar(ctr+3). I just want to know the possibility of same for layers.
 

You want to create a new tool palette for layers?

Use a LISP/Macro to your palette and have it just insert the drawing that includes all layers/styles and have the command cancel after the definition is inserted, but before an actual object is.eg.(command "_.-insert" "MyLayerFile.DWG" nil)This will import all layers/styles (the block definition, etc.) but it will be cancelled before the option to insert an actual object in the drawing. I used to use this method for some LT users.

Thanks for the tip. I didn't realize you could do that.