Just don't do anything that a professional *should* do that is going to be noticeable by an inspector.
I hate to hate on people who DIY a lot, but frankly there's a reason you don't get paid for your ability to paint a wall - you're bad at it (informal you, i have no idea who you are and what your painting abilities are)
If something needs to be professionally done, please get a professional. You're hurting the resale value of your house if you think you're a good electrician.
For the walls, all I can say is don't put a bunch of shit up on them just to take up space. When my wife and I first moved in we had the same problem - what do we put up there? We have friends who have decorated like hell but their wall is just a bunch of consumerist shit 'Happiness is a Glass of Fine Wine' in woodcarving on the wall - OK great.
What we did was just buy things / make things that happened in our life, such that our decorations are all actually telling a story. It's not that hard - find pictures and frame them - go to a painting class and display a side-by-side recreation of 'The Scream'. We also tend to buy local art when we go on vacations, and have big events (Winter olympics was ours - tickets + poster) immortalized by getting them framed / shadowboxed.
Our house was barren about 4 years ago on the walls but now we're almost running out of space, and everything that 'decorates' is actually something that pertains to us, instead of 'Home is where the Hearthstone Is'.
Also if you're into wall decals:
http://www.whatisblik.com/