Add your icon.png to the src/main/resources directory of your project
Recommendations
For best results your icon's dimensions should be exactly 80 by 80 pixels. If it is larger or smaller than the required sized it may be scaled
For the icon to be displayed, the user must have Bamboo 3.4 or above installed. For developers writing Tasks that target Bamboo 3.1 and above, defining an icon will not cause versions Bamboo 3.3 and below to break.
Atlassian recommends that icons should be transparent and not filled white. Transparent backgrounds will allow your icon to be displayed on other parts of the user interface in a way that is aesthetically pleasing.