I'm not sure what you mean by "with more detail", but good free pixel arts programs are Piskel and Aseprite, which i enjoyed using a lot. Although Aseprite costs 15 dollars, there is a free trial period.
As for getting your group to work on your game, check the faq section on this topic here: https://www.freemmorpgmaker.com/docs/en/FrequentlyAskedQuestions.html#page_How-can-I-make-it-so-other-players-or-designers-can-connect-to-my-server-to-play-or-help-design-my-game