A while ago, I saw mosaics created of Rubik's cubes on the internet and as a cube-enthusiast I wished I could make/have one myself. However, there were two obvious problems:

1. You need a lot of cubes, which means it's going to be very expensive.

2. It's going to be very large and you have to find a place for it.

But there was a solution to both of these problems: Ordering 3cm x 3cm x 3cm (1.2" x 1.2" x 1.2") cubes in bulk. I got 600 cubes for about $100 (including shipping) from china. It's still a lot of money but doable.

I was kind of in a rush so the documentation is not as good as I wished but I thought the result was shareworthy.

Step 1: Planning

Before you start, you should consider:

how much detail the image should have,
how large the image is supposed/allowed to be.
what your budget is.

Detail: Each cube gives you 9 pixels, so my 600 cubes would give me 5400 pixels, which would be enough for a 90*60 image.

You also have to consider that you only have 6 colors so you have both a very low resolution and a very limited palette.

There are tutorials for converting your own photos to suitable images on the internet. I used the GIMP tutorial on http://www.youcandothecube.com but ended up using their example for 400 cubes (pdf) for two reasons:

I was in a hurry because it was a Christmas present for my girlfriend.
I wanted to use a photo from our trip to the US and would have ended up at pictures of the bridge anyway.

I think another good motive would be images from vintage video games because they are pixelized anyway!

Size: If you buy the 3cm x 3cm x 3cm cubes, resolution translates directly to size so that part is pretty easy. You probably won't have the problem that the whole thing is to small.

Budget: Look around for deals from wholesale sites. 600 cubes was actually the smallest amount I could get for

When ordering keep in mind that if you pay cheap, you get cheap. I got very low quality cubes (many many just disintegrated in my hands) and I think I lost about 30 cubes that way. However, about 10% of the cubes were quite high quality (definitely from another production) so you might also get lucky. I would recommend to buy at least 10% more than you need.

Step 2: Planning Contd

Now you have to decide how you will get the cubes on the wall. My main concerns were:

I didn't want to glue them because I wanted to keep the option to change the picture
I didn't want to use a frame because I wanted the sides to be visible
I didn't want to have glass in front of it because I wanted to keep the texture

My solution was to tie them down using nylon string while supporting them with an angle bar from underneath

The materials I used were:

Cubes (obviously)
A board of the right size
Nylon string (I used 0.15mm width). If you do it like I did, you need about 5 * (cube width) = 15cm per cube plus overhead (I think 20cm per cube should be plenty)
angle bar + glue
Wire to hang it on the wall (you should probably also support it from underneath because of the weight)

The are very few tools required:

electric drill
needle and scissors for the nylon string

Step 3: "Solving" the Cubes

Now it's time to make the actual image. This is going to take some time. It is easier to do than a normal cube because you only need one side but the low quality of the cubes made it a lot harder to turn the cubes. I think, it took me a little less than a minute per cube. Of course there are parts of the picture that are a lot easier and sometimes you don't have to turn the cubes at all.

Step 4: Assembly

Drill the holes and attach the angle bar. You want the nylon string to go through the grooves so drill the holes as indicated in the picture.

"Sew" the cubes on. Be especially careful with the edges. A lot of the times, my wire would become very loose because it slipped deeper inside the grooves. I did 5 cubes at a time and used adhesive tape to hold the string down on the back side.

Attach something to hang the mosaic on the wall. I used wire that I put through the holes before I sewed on the cubes.

This step took me almost as long as solving the cubes (that string is practically invisible in bad lightening). If you choose another method like gluing them down or building a frame with glass front this will be much faster.