Unfortunately, this site does not allow for me to give you specific tutorial-like instructions, but I will try my best to give tips and address some of the problems that will pop up.
Okay, for one, you are incorrect when you say
This means that the traditional "start with the face, then work your way back to the neck" style of facial modelling doesn't work effectively.
starting on the head will work effectively, it just needs to be adapted to fit your needs. The mesh primitive you'll need is the cube.
Subdivide it twice in edit mode with "smoothness" turned up to 1.00.
I don't know why my image is skewed, but that's (almost)what it will look like.
You can use "Import images as planes" addon to put in your concept art.
By modelling the head separate from the body, all you will have to worry about is connections. Snap to vertex will be optimal for joining them.
another of your favorite tools, especially on joints and such, will be Ctrl + V > smooth vertex. this gets rid of nasty sharp angles.
Remember that when you model limbs, you will want to extrude the selected faces all the way to the end, and afterwards add loopcuts for detail.
The hands will be the hardest, just make sure to turn proportional editing to "Connected", to avoid screwing up the other fingers.
I used a mirror modifier for all of the modelling until the end when I applied the modifier and extruded an eye.
I wasn't trying to do the work for you!! but in questions like this, unless you state specific problems you run into, it's very hard to answer without going through it yourself. Heres the base-mesh I made if you want it.
Honestly, kudos for trying, but modelling your wrappings as part of the mesh is a no-go. You can either use brasshats idea of extruding a plane, or you can sculpt them on using Clay strips, Crease, and Flatten brushes. In order to do these wraps, you have several practical options.
Heres the best way i was able to find while making wraps.
Turn on face snapping (Shift+Tab).
Left click on the model to place the cursor there, now add a plane. delete all but one of its edges. you will now need to extrude the remaining edge around the head in the place that you want the wrap to be. Don't worry if it looks like crap and won't stay on the outside of the mesh right now! We're gonna fix it!
The modifier stack you'll be creating today will look like this.
The subdivision mod adds more vertexes for the others to work with. The Shirkwrap mods target is set to the mummy, and causes the wraps to follow it closer, just like ceram-wrap in the microwave. Lastly, the solidify modifier adds thickness to the wraps.
You can now go back into edit mode to fix problems. Any parts where the mummies head is poking through can be fixed by adding a loopcut Ctrl+R.
Now you are ready to add more wraps. repeat the process with varying thickness on the solidify in order to swaddle your mummy.