Simulating a melting picture using nParticles

[niurna]

I'm trying to use nParticles to simulate a melting picture. As shown in the attached graphic I've been able to emit particles based on the colors of the various pixels

However I'm having difficulty doing the following:

The emitted particles should stick to the surface of the image and not to pop out.

Merge the particles into a smooth surface

Have the smooth surface retain/reflect the colors of the various particles

Many thanks,

Justina

[niurna]

Update:

As shown in the above image, I've been able to figure out how to make emited particles stay on the plane of the image and spread downward by making  particle goal is the surface from which they are emitted. Unfortunately, the particles are clumping on the floor at the base of the painting. I would appreciate help making the particles to spread about the base of the painting once they reach the floor. 

I still don't know how to merge or convert the particles into a smooth surface for rendering. This smooth surface should retain the colors of the various particles.

I've uploaded the scene shown in the above screenshot, including the image that I'm trying to melt, as a zip file to: 
http://proceduralcg.com/wip/Scene.zip  

Thanks.