Members have very kindly shared some of their restoration tips. Do you have anything to add? If so email me the details! (Photos max 500kb, if possible)
Pictures below courtesy of KT Miniatures ©KT Miniatures – 2009

There are several different methods of aging paintwork. I prefer to use acrylic paints. These are useful to age over a brand newly painted surface. I can recommend the colours Raw Umber or Burnt Umber particularly. However, dilute well with a lot of water so that it constitues a weak wash and brush on sparingly. Dab excess off with kitchen towel & the residue left behind will make it look like it has been there for decades! 
Add extra to nooks and crannies where it gets dirtier naturally. This is a light covering and will not ruin the fabric of the dolls house but is very effective. Can also be used very sparingly on brand new wallpaper too (but not antique wallpaper)! The good quality acrylic paints come in tubes and are generally available from most good artshops. They are water based so you can wash brushes and paint off hands with soapy water. Plus also of course, you can gently sand newly painted surfaces with a fine grade sandpaper.
The Farrow and ball paints are perfect as most of the colours are taken from original paint in ancient houses. These can be bought in sample pot sizes so no need to buy large tins.
When the house is painted if an older look is needed you can use a furniture polish in an oak colour, but be aware once that is done you could not change it if you did not like it. I did a small early Victorian house this way and used Farrow and ball DRAB paint, this is a perfect colour for Victorian houses.
Their Calke green and Sugar bag blue are perfect colours for painting kitchens.
1. By Celia Thomas:
I use Adobe Photoshop Elements. Scan your remnant in, then in Photoshop, cut out using the Crop Tool the best piece of the pattern on screen.
The easiest way is to formulate it into a square, then replicate side by side, row by row until you have enough to fill a sheet. If you are lucky with the pattern, some lend themselves better than others, it can work well. However on some intricate patterns, it will not be an exact match but could be acceptable.
When you become more confident with the tools on Adobe, you can do allsorts...and more intricate procedures......it is actually quite good fun and amazing what you can achieve!
2. By Beatrice Dassonville:
I suppose , there are better ways to do than mine, but that's what I do:
I first make a picture of my paper, select the part I want to use, and which is the smaller part of the design, I create a .jpg file.
Then I use Word. I create a new document. Then I select the .jpg file. I paste it. Change the size of the picture in Word, in order to be at the right scale. And then copy, paste, again and again, until the page is full.
I hope, it works for you.
3. By Linda Bancroft:
My son prints papers for me:
He scans a good segment of the pattern and then copies and pastes it next to it, and again until you have built up the width you need. You do need a piece that is a consistent colour to do this. Hope this helps in some way.
1. By Marion Martin:
In one of my houses some of the glass was not fixed into place on the window frames. I pondered for a while then came up with the following idea:
I cut some 1/2" panel pins in half and used them to refix the window frames where the pins were missing, a right fiddly little job!!
3. By Wendy Gater:


(Above: Pictures Courtesy of Wendy Cairns - Mirror before and After)
If you have a miniature item with a missing mirror you can use a new mirror and to achieve the "aged look" the trick is to scratch the mirror backing, right down to the glass, use a blade with a sharp point so that you can make little round holes and sand and scrape until you get the desired effect.
Use black paper or card to back the mirror or you can paint it black, this is what gives it the aged effect.
I regularly frequent charity shops, it's amazing what you can find, I hunt through the material, placemats, cushion covers etc, when looking for an item if you like it but think it may look to new, put some teabags in a bowl with boiling water then leave the items, checking regularly to see how much colouring has taken, cotton, lace items grab the added colouring very quickly some items take a bit longer. The achieved change of colouring can be as weak or strong as you want it to be.
Cushion covers especially tapestry or embroidered ones make excellent carpeting in an old antique/vintage house when cut to the size required.
I have also dabbed tea bags onto matt paint that I have had to add to a Dolls House if the original paint is not present. Dab the lightly squeezed teabag onto the paint but just do a little at a time then let it dry to see the actual colour that has been achieved.
(of Ty Bach Twt Dollshouses & Accessories, North Wales)

(Above: House before removal of overcoated paint)

(Above: House after using tip below to remove overcoated paint)
A way to remove overcoated non gloss paint is by using nail varnish remover, apply using Q-tips (cotton buds) it takes alot of time and a lot of Q-tips but as you can see it's well worth it from the pictures above.
It's always best to start in an inconspicuous area of the house, just incase things go wrong.
A way to make it easier to remove wallpaper that has been papered over the original Dolls House wallpaper is to use a hand held steamer, these can be bought in general D.I.Y. stores often used for cleaning ovens etc.
Hold the steamer a distance away from the room and spray gently, do not place the steamer to close. Then you will be able to carefully and gently remove the added wallpaper to reveal the original paper underneath that is remaining.