This is one of my favorite things to do... come up with decorating ideas for small spaces with a REALLY small budget. Rooms that not only look good, but are functional and don't look like they were decorated on the cheap... even though they were!
These ideas are for a 10 x 10 bedroom with one doorway, one closet and one window and this is also assuming you have nothing to start with i.e., empty room and nothing to put in it. Something similar to below:
To begin, the bedroom wall colour should be a neutral colour. Something like beige will grow with them and when their tastes do change, you can modify a few accessories to their new likings and completely change the look and feel of the room. For example:
Lets begin with the bedroom furniture essentials i.e., a twin bed, a small-medium sized dresser, a side table, a lamp and a pair of curtains and curtain rod.
1- Buy the bed frame, dresser and side table second hand. Sites like Kijiji and Craig's List and stores like Goodwill and Salvation Army provide lots of durable, solid wood options at extremely reasonable prices. Regardless of where you purchase the items, you should paint everything the same colour (I like cream but any neutral colour would work) to help them coordinate.
2- The new, twin mattress will be the most expensive thing in the room. If someone could give you a mattress that would be ideal, otherwise, you can buy the mattress from JYSK. Something like the Paradise 6" memory foam mattress. It is extremely comfortable and a reasonable price ($169 plus tax). You can find mattresses (especially foam ones) for less, but they will be less comfortable and will wear out faster so you will end up spending more in the long run. If the bed frame you buy does not have wood slats (the alternative to a box spring) you can simply make your own wood slats from free pallets available at most big box stores.
3- Purchase the bedding (and pillow) from Walmart. You can get all of the bedding for under $40. The sheets should be something 100% cotton and a neutral, solid colour. Since kids tend to sweat when they sleep, a neutral colour, cotton blanket is more then enough bedding (plus the sheets of course) for them.
4- Buy the lamp from Walmart where you can get a simple cream lamp with shade for $10 plus tax.
5- Buy the curtains from IKEA. Something like the VIVAN cream curtains for $15 plus tax. You can find the curtain rod kit (rod, bracket, finials) at JYSK for less than $10.
6- To paint the room and its contents you will need 1 gallon of wall paint, 1 gallon of paint for the furniture and 1 quart of chalkboard paint... plus the painting supplies to go with it. You can buy the paint brushes and mini rollers at the Dollarama but the large rollers you will have to buy at a big box store. For the chalkboard, simply use tape to create a frame for it.
7- The full length mirror can should be purchased at XSCargo. They sell them for $8.
8- The two medium-large picture frames (with mats) should be purchased second hand. Simply paint out the frames to match the rest of the room. Add scrap-booking paper and coloured tape to the frames to give them a little individual personality. The pictures or small posters can be printed off at Walmart or Staples for a small cost.
9- Purchase the small storage boxes or decorative accessory and plant pot at the Dollarama. Paint them to match everything else in the room (if necessary).
10- Purchase the plant itself at a big box store where they sell for $2.50.
11- For the wall hooks, buy the hooks themselves at the Dollarama (2 hooks x $1.25) and the piece of wood to mount them to at a big box store (where they will cut it for you) and paint it to match the room.
12- Buy the pillow fabric and fill at Fabricland (on sale or from the ends bin) and make the pillow yourself.
solid wood bed frame $50
solid wood bedside table $15
solid wood dresser $50
twin sheets set $20
twin blanket $20
curtain rod kit $8
Accessories- lamp $10
picture frames (with mats x 2) $10
scrapbook paper (x 2) $2
coloured tape $2
hooks (stainless steel x 10) $6.25
plant pot $1.25
full length mirror $8
storage boxes (x 4) $5
pillow fabric $5
pillow fill $5
-Total budget- $404
... which sounds like a lot but if you didn't have to purchase the mattress it would only be $235! That's pretty good for a fully functional and nice looking kids room.