Status icon modification

[fmgrowit]

I'm self teaching/learning this program so bare with me. If my questions sound mis-directed, feel free to steer me in the right direction.

Currently, I'm working on making new icon images. I'm assuming that since the icon is an image, all of the commands for each image are relatively fixed, so if I assign a new image to the "Contains unread forum posts", the script will not change and that icon will simply replace the default icon.

So, my dilemma is...I don't know how many icons I need to replace nor do I know the definitions per icon. Is there a list of default icons with definitions? The basic color themes will be maintained in the new icons for a consistency with default icons due to the familiarity users have with the meaning that those colors represent...a sort of standardization.

Another, but related question is;
The default "green arrow" icon appears with the status icon in threads where "You have posted in this thread". Is this a separate image or do the "Contains unread posts, Contains no unread posts, Hot thread with unread posts, Hot thread with no unread posts" images have to contain the "You have posted in this thread" indicator within that image? (green arrow)....or is the "you've posted here" indicator an overlay?