Is there a way to use my own play button image that is superimposed on the poster image or hide it so I can put that on my poster image?

Hello Michael,

You have a choice on that:
1):
You can edit the original image used for Play button. It is located in SiteRoot/Styles/dmxHTML5VideoPlayer/styleName/start.png.
And 2):
You can change the style property for that background image by setting up somewhere following css statement:

.ppstart{
    background-image: url("your_new_start_image_relative_path_here.png") !important;
}

Regards,