How can you possibly think you need more practise! This is wonderful, not only have you got the elements of a creature of slanesh (though i am not expert on warhammer) but you have your own distinct style as well. The contrast with this beautiful and dangerous creature and the grimy war torn battlefield work very nicely together to at first draw the eye to the sensual being and then as the feeling of unease develops as the viewer realises this creature is not quite as beautiful as first thought the eye moves to that grimy battlefield of blood, death and barreness exagerating that feeling of unease. It is contradictory to the initial sensuality of the being due to its barren aspects. Which I feel is exactly what you are wanting to create with any creature of slanesh. the colours are perfect and i like the atention to detail that shows you know the character well such as all the little symbols and colours themselves. Basically this is the long way of saying i think you have done a really good job!