Ok, now lets see what we can do about emulating this effect.
We need a few elements:

• Balloon color texture.
• Balloon transparency map. (to make the wires/seams less transparent)
• Bright light source with high falloff.
• Blurry transparency.

Ok, first lets put the color texture of the balloon into the diffusion slot of an empty texture. This will be the base of the balloons texture.
Now we need the balloon to be partially transparent. I know it sounds bad, but it'll be the basis of our translucent effect. Lets put it 30% transparent for now, or use the transparency map to control the transparency.
Make sure there's no ambience or specularity, and no reflections, metallicity or bumps yet. Exit the material editor.

Now place your light source at the position of the flame, and turn the sunlight off, or use a bryce night sky, either way, make sure the flame's the dominant light source.

Now try a square falloff on the light first, it's the most 'true to life' and thus probably a good starting point. Up the light intensity, and play with the lights color a bit to get a convincing light color. notice it's light color I'm talking about here, not neccesarily translucence color.

Now comes the magic, when u have the light shining through looking good. we go to the premium render settings and we turn all premium effects off, except blurry reflections. Change rpp to a low setting for test renders 4rpp-16rpp will do just fine.
Blurry reflections can blur out whatever shines through the transparent surface! thus making it look translucent. It's a powerfull method to simulate translucent surfaces! To control how much the amount of blur, sue the specular halo color in the texture of the balloon. The color can also be used to adjust the translucent color texture, but probably its best kept colorless. feel free to try otherwise though.
Once the effect is the way you want, witch to the lighting u want in ur final scene, and tweak the diffusion intensity and transparency to something that looks like a good balance.
I think something like that should most likely work a treat.

(_/)
(='.'=)
(")(")This is Bunny. Copy and paste bunny into your signature to help him gain world domination.