Lava

1)Create a new file , choose a orange and a black colour and then Filter--Render--Clouds:
2)Go to Filter--Artistic--Watercolor with this settings : Brush Detail 9 Shadow Intensity 1Texture 1

3)Apply Filter--Sketch--Chrome with Detail 6 and Smoothness 2.
4)Now press Ctrl+U and put some colour (choose colorize and use Hue 20 ; Saturation 100 and Lightness 0)

5)Now go to Filter--Artistic--Plastic Wrap with the following settings : 7 ; 7 ; 6 ; Final result :