In my 2 years of playing Skyrim I never really used Light Shields, I normally just run with Heavy Shields even on Light Armoured characters. If you use Light Shields, please tell me why you use them. :)
I use light shield on light armoured characters just because I have the smithing perks to improve them more. I usually have mixed light and heavy armour so I just choose a shield that looks good with the rest of the armour.