Create a Mii Character Online

Mii Maker

With the mii creator you can customise everything about your character and create the perfect avatar - whether that's a boy or a girl. The Wii Mii maker allows you to choose from a wide variety of options for each facial feature. By the end of the design process you will have created a carbon copy of yourself or something completely different!

Make Your Own Mii Now (Desktop) Create a Super Mii Character (Android)

Mii Maker Online Get's Taken Down!

ninteno wii u mii maker

While there are not many editor tools left online to create your mii, the flash one still is available.

Nintendo's official browser version which you could use on your laptop/pc seems to have been taken down as we can no longer access it. Instead it seems they only have a guide of how to make your own Mii using the Nintendo Wii U or Switch here. This ia actually a better version than the flash one but requires you create an account to use it.