Hi there,
Free templates as in general purposes templates or specifically usable for mailwizz?
If for mailwizz, i don't personally know of any, i believe whomever modifies the app look will do it for his own company and will not be willing to share.
However, i know of one person who did some nice changes using only css, will have a talk and maybe i can create a free theme out of it and share it here.
Thanks
