Those project tab play and pause icons are build in, working in any theme. Not saying there wouldn't be, but I don't know of any separate image files available for them. Maybe some day there could be images like tab_play and tab_pause, like there already are tab_down, tab_down_sel, tab_up and tab_up_sel images for the themes.
Only a dev version feature at this point anyway...
How to modify the project Tab play button.
Linear Mode
