You might wanna look up using some sort of sprite sheet to make the animation for the fire and make it play the sprite like a GIF using some modules/scripts. Should give you the freedom of having the style of fire you’d need as long as you know where to find them or know how to draw them.
Here are some modules that might interest you:
- SpriteClip Sprite Sheet Animation Module
- SimpleSprite | Create spritesheets for UIs easily!
- SpritesheetVisualizer 1.0 - Easy gifs for your games!
Or you can try to use particles in the GUI using some other modules such as rParticle or UIParticle which should just give you somewhat the same look as a normal 3d particle, though might be a bit harder to mimic the style you’re looking for.
I have not used any of these modules personally, but I think it’s a good place to start looking.
Hope this helps, cheers.