Yes, there is! Add a new emitter from the preset "Basic > Static Sprite". This emitter is a dummy object that emits a single static particle serving as the background image. Then you can choose the image you want the sprite to have under the "Material" property of the resulting particle type "Sprite" (click the small settings icon on the right). Now make sure the sprite is large enough to fit the entire screen by adjusting the "Initial Size" or "Size" property. If the static sprite appears to occlude other particles, make sure its "Layer" property is set to 0. Finally, render and export the effect as normal. Hope that helps!