Is it possible to change the default flags in tmux window-format?

Question

I'm trying to customize my tmux environment. I'm now working on window-status-format and window-status-current-format. The default is: #I:#W#F but I'm wondering if these default values could be changed in any way.
For example, instead of arabic numbers in #I I would display roman numerals or, more important, instead of the * (that is the default flag for current window) or - (default flag for last used window), I would display other symbols.