Hi. More photos of the whole space would really help people to give proper suggestions, so give us some when you can. You have white, cream, grey, brown and black, from what you've told us and this pic. The grey could be the only jarring colour, but we need to see more. Well, at least I do before I suggest the backsplash tile colour and style and size! You can have stoves re-enamelled, but it could look great as is. Cleaning? Oven cleaner, elbow grease, washing up liquid, proper scourers - for the inside, that is. An extractor fan on a traditional stove with a sideways flue is going to be tough. Normally, you'd put this in a chimney breast or what looks like one. Anyway, post more pictures (and reassure us that you are going to move those sockets) and then I'm sure you'll get lots of great ideas coming your way.

Personally I wouldn't go with a yellow splash back. Not because it wouldn't go but more that you already have enough of that accent colour around the room, over do it and it can look forced. There is a fine line between getting the balance right were it looks classy and going over board to the point it looks naff. Personally I would either go for a splash back that is colour matched to the walls or a smoked mirror. You are limited in some ways because it appears there wasn't any forward planning with regards to splash backs. Any splash backs would need to be confined to the width of the extractor because your curved wall units won't open otherwise. They would have to be packed off the wall if you wanted to go full width splash back. I would recommend a durable matt paint in the kitchen. Good quality ones will withstand washing without polishing up and showing tell tell marks where they've been washed. Little Greenes Intelligent Matt is perfect for this and is our choice of paint when not using any further splash backs above the granite upstands. I understand a colour matched glass splash back or smoked mirror may seem like the safe option and boring to some, but there is no point in being brave just for the sake of it. You've got plenty of other points of interest in the room with regards to colour without having to push it too far. Let the kitchen itself be a subtle canvas to show off other items rather than fight with them for attention would be my advice.

Here is a photo of the mirrored splash-back in situ. It cost £230 which included the templating and fitting. I would recommend having the glazier do the templating and fitting as they should then take responsibility if it subsequently cracks within a couple of weeks of fitting...this happened to us and the glazier came and removed the cracked one and replaced it. Apparently it can happen if the fit is tight around the cut outs. We are really pleased with it.

Have you thought about getting mortex to use on that area - it is like a plaster effect but it gives a concrete look which would work wonderfully on that area with the mood board colour and textures you have in mind. It is waterproof and very easy to wipe clean. Search it on Pinterest - it looks very different and more interesting than your average glass or tile splash back.