Hi.
What you have to do is to add an Image Widget to the design and set its Mode property to Threshold.
Threshold mode works in this way: you have an animated picture made of 2 or 3 frames.
In normal conditions the first frame of the animated gif is shown.
If a certain condition happens, for example fuel is low, the second frame of the picture is shown.
If you set "Alternate pictures" property to TRUE, the second and third frames are shown alternatively, when the condition happens.
In your case you need an animated GIF with 3 frames:
1) first frame is blank. this is what is displayed when the fuel is NOT low
2) Fuel symbol as the second frame
3) blank frame as the third frame. this way when second and third frames are shown in sequence, you have a blinking effect.
To create the animated GIF there are many tutorials and software around. I use Easy GIF Animator. it's not free but maybe there is a demo around...
I have attached a design file with the things I have described.
The fuel symbol will blink when the fuel is below 10 L.
Please let me know if you have more questions...
Cheers
Cristiano