Nope. This pic's perfect, I would change nothing of it.The vector part gets well into the raster part. Ponies, which are extremely well defined, stand out nicely; while the background softly accompanies them.It's perfectly done.From another point of view, choosing if putting vectors in a pic or not also depends on your skills, the time they require and the amount of effort you usually put in making them.Sometimes, drawing raster is quicker. But vectors allow to get amazing results, let alone the infinite resolution they can give.But, of course, I'm not the one who should say these things. You are the vector master here