Shorts are not acceptable.
Wearing ties or bows is not a problem.
T-shirts are acceptable.
Obeying Islamic rules including Hijab or Islamic dress-code is necessary in Iran. (usually in a kind way) to make it correct.
There are some minimum requirements for foreign women dress-code in public places
*. Color : It`s a completely false belief that wearing must be dark in Iran. There is no limitation in this respect and we recommend you make sure using light colors in summer.