So here's the info on how I get the images onto the wood. The short version is I hand paint them on. I'm no painter. I can't draw. But I can trace. And I can paint within the lines. 
I discovered this great item called 'Graphite Paper' at Hobby Lobby. ($5) You can buy it online if you don't have a hobby store near you. 
It's like tracing paper. I print out the image I want with a regular inkjet printer, put the Graphite Paper under the image and take a pen and trace all the lines on the printed image. It transfers onto the wood with nice dark lines that I paint. 
Here's a few pictures that might better explain the process.

That black paper (under Mr Monopoly there) is the graphite paper. Graphite paper has two sides. The shiny side goes down. You can re-use graphite paper a few times before it's used up. The images you traced will stay on the shiny side but do not transfer to a new image. It comes in two colors -black or white- on wood surfaces the white doesn't show up well, so use the black. But on dark painted surfaces the white is the way to go.
In the other two photos you can see the lines left behind after I took a pen and followed the lines on my printed image. And the last picture shows how it looks after I painted in those lines.

I keep the used printed image close by for reference because sometimes it's not clear exactly which lines I should be painting in. 
I use basic black Acrylic paint - found at any store that sells any kind of craft stuff. I don't have a brand name preference. Acrylic paint dries almost instantly so I don't pour much out to use at a time. Just a small dab. The larger bottles might run you $3-$5 and the small ones are priced under $2. 

I save lids from around my house to use as a paint tray. Lids from soda bottles, milk cartons, juice drinks... it's a nice way to reuse them and I find they're easy to move around my project as I work. Since the paint dries fast I usually have to add more paint to the lid, or toss that lid and get fresh paint quite often. If you're painting and find that you can't seem to get the paint to 'behave' -- like it's sticking to the paintbrush and won't adhere to the wood -- that's when you need fresh paint. 

I buy not-too-expensive artist paintbrushes at the hobby store to paint with. They run me about $8 for a set of different sizes. You'll have to experiment to see what style of brush works for you. Long thin bristles or short pointed tips... it's all personal preference at that point. Personally I like a shorter length handle with very pointed synthetic bristles. But I also like the square flat bristles for certain areas. Figuring out what works for you will take some practice.
I try to do long straight lines in one stroke, and I hold my breath while I'm doing it (consider that part optional). And I paint from left to right because I'm right handed, and I don't want to smear what I just painted.
A steady hand helps, and of course a comfortable work area. I paint indoors. Sometimes at my kitchen table. There's no smell from the artist acrylic paint and as long as you cover your work area with a drop cloth, you're fine. Since I only put a dime sized drop of paint into the lid (doesn't sound like much but it goes a long way) I can't spill and do too much damage. 

By the way, the images that I've used on my own furniture and artwork are images I downloaded from the internet that I fell in love with. Some I've modified a bit to suit my needs, but I still don't claim them as being my art. Since they are for my own use and not to make a profit (I don't sell my stuff) it's not a problem. But if you're hoping to sell your creations I suggest making sure your images are royalty free. The Graphics Fairy website has tons of free images that you can use. She also has a few other transfer ideas but none of them has worked for me. I admit I don't yet own an overhead projector to put the images where I need them, so that method may work for me too. But for now, graphite paper to transfer the image has been the easiest method I tried. 
One thing about graphite versus overhead projector -- I can stop and start my painting when it's convenient, with the overhead you might have trouble lining up the image perfectly again if you had to stop.  
I know that painting on such a small scale - slowly and carefully - would drive some folks nuts! But I enjoy it. 
Please visit thegraphicsfairy.com - you won't be disappointed! 

After the acrylic has dried for 24 hours, I've used oil based wood stain right over the painted areas and had no issues. The same about polyurethane. Or wax. I've used that too. Although the wax can leave a bit of a whitish haze over larger painted areas, it just means you need to buff that area a bit more aggressively. 
If you want more information about the products I've used please check out my Paint, Stain, Polyurethane & Wax Page 
Lastly don't forget - have fun! :)