@ Mecha-
To merge a mesh in Zbrush go to your Subtools panel, you should see all your seperate meshes there, under the tools themselves there are a few menus you can extend, one is called Merge, it has a function called merge down that works just like it would in Photoshop, so merge your tentacles down into the face Subtool and then run a dynamesh or a Z-remesher to mesh it all together.
@ Rapture- Even when working with a handpainted style you're going to want to use some references from here and there, first thing that bothers me is the way the cracks look, they are very unnatural.
Secondly something you'll want to do with your shadows, I see you're using very dark de-saturated colours for shadows but what you actually want to do is make sure to saturate the shadows more so than the base colour of the brick, this will alow you to also make the shaded areas slightly brighter than they are now.
Posting a picture from my portfolio here, this is from a game we developed called When Imps Fly.
If you have a peek you'll see what we don't use any black in our textures, it is all just darker more saturated verisions of the base colour, hope that helps!