How do you make an icon for health? I want it to be sonic style with a tails icon like this 
how do you do that?
There is a Flowlab Help section that will answer most of your questions.
http://flowlab.io/resources
On “Video Tutorials”, you will find a series of videos explaining how to make a platformer, including how to add an Icon for health.
There is also the “Helpful Examples” section where you will find 2 examples on how to display the player health on the User Interface.
Heart Example:
http://flowlab.io/game/play/300856
Health Bar Example:
http://flowlab.io/game/play/9822
There are two examples that show you how to make a health icon.
Health Bar Example
Advanced Bars
If these aren’t necessarily what you are asking for, try doing something like this:
Make a user interface object that keeps track of player health. Give that object an animation showing off the health of the player (like one heart, two hearts, three hearts). Then, when the player takes damage, a number behavior with the value of -1 adds to the value of another number behavior (that number should be the same number of frames for the health animation). That number behavior will send its new value into the “go to” input of the animation behavior.