Create Crosshair & Hitmarker
Create your own crosshair and hitmarker by using the graphics editor that supports transparent background. (ex. Photoshop / Paint.NET / Pixlr) I am using Paint.NET.
Make sure that background of your image is transparent. Otherwise, the crosshair and hitmarker will have white background in game as well. However, If you want the background, you don't need to make it as transparent.
Also, make sure the color of crosshair and hitmarker are white. Otherwise, when you change color of them in Bounters setting, color might not change well.
Save it as .png file for transparent background.
Put crosshair image into 'GameData/Crosshairs' folder, and put hitmarker image into 'GameData/Hitmarkers' folder.
Now, go into Bounters Settings, and click 'Game'. Scroll down to Crosshair & Hitmarker section and you will see your custom crosshair and hitmarker. Click to use it. Color and size can be customized as well.
[Note: The crosshair that I created in this tutorial is not included on release since it was created just for the tutorial.]