Yes, I was missing the highheels too. How to change the footpose is almost the same as the handpose (Please compare when you miss a step). But now you have to customize your shoes.
My way (using MH1.1, Blender 2.76, Avastar 1.59):
1. Model your avatar in MakeHuman, apply an expression, add clothes etc. Now export (.dae) this avatar twice: with the opensim-rig and with the default-rig too (with toes).
2. Model shoes or import shoes into Blender (hope some creators will help with blendfiles). The sandals in this tutorial were created by Taarna Welles for OpenSim (thank you very much ) Export your shoes as .obj. Close Blender.
3. Now first import your avatar with the default-rig into blender, select the avatar.
4. Select the rig.
5. Activate X-Ray
6. Choose Stick (easier)
7. Now import your shoes
8. Select Pose Mode
9. Select the transformation-rotation (curve icon)
10. Now rotate feet and toes.
11. Return to Object Mode, select the avatar's body and export it as .obj. No need to save shoes, eyeballs or tongue.
12. Important: Save this avatar as blend-file too. Maybe you'll need him later to create more heights or handposes. Close blender.
10. Open blender once again. Now first import your avatar with the opensim-rig. Use the Avastar-transfertool to get the Avastar-rig.
11. Next import your obj-avatar with your new bended feet. Open the toolshelf and rotate the avatar.
12. Now select the armature and your new avatar, press 'Bind to Armature', delete the 'old' avatar.
13. Import your obj-shoes once again and 'Bind to Armature'. It seems that there is no need to rotate the foot-bones. Mavbe this will even destroy the Avastar-rig. Export, upload. For me the tested animations worked well without having modified the footbones.
14. You can upload the shoes separately from the body. Rezz the avatar inworld, add the shoes and link them to the body, then wear your avatar with shoes.
Have fun and be creative!