Edible painting pens and biscuits

If you cannot find these ingredients, it will be hard to get this type of icing made.

The first thing is the liquid glucose. If you used any old thing labelled "syrup", chances are that it contained water, and this is what made your mix a sugar. Liquid glucose is mostly sugar, with almost no wetness to it. Substituting something very wet will not work.

Things which will work instead of glucose syrup are agave syrup, treacles, corn syrup, mollasses, golden syrup and honey. You should be aware that most of those will give you a more or less strong coloring and will have a bit of taste on its own. It depends on the type of your cupcakes whether the taste fits them. Corn syrup and golden syrup will be the best alternatives, but they are also less popular around the world.

The other thing is the sugar. It absolutely must be in a powdered form. Crystals won't work. If you have a food processor, just put the crystalized sugar in there and process it. Use it immediately, or it will fuse together due to air moisture.

But you may still be able to find icing sugar. It is just another word for powdered sugar, and it is used in Middle Eastern cuisine (your profile says Lebanon), for example for dusting lokum, but also in some halva recipes. If you can find a confectioner who does these things, you can ask them for a source of powdered sugar.

If you cannot find ingredients which produce an acceptable quality of icing, you can also try other types of icing recipes for decoration. Most do use powdered sugar for easier incorporation, but some are made with sugar dissolved in a liquid.

Part of the problem is that whole wheat flour goes rancid pretty quickly after it's milled (I believe it's from the natural oils in the germ). The usual advice is that whole wheat flour has a shelf life of six months or so, much less than white flour. If you're using old flour, try getting fresher stuff.

If you're willing to go through extra effort, consider milling your own whole wheat flour; after reading this article: http://www.realbakingwithrose.com/2006/11/rose_levy_beranbaums_100_whole.html I got a grain mill attachment for my KitchenAid mixer and started milling flour, and I've become a total convert. Fresh-milled whole wheat flour has an incredible taste. My standard loaf these days is 50% whole wheat and 50% bread flour, and it tastes great. It has a nice nutty flavor without the tree bark or cardboard you'd normally associate with bread with so much virtue in it. I've done 100% whole wheat loaves before, and while they're very good, they're just not my thing.

If you want to get even further into it, Peter Reinhart has a book on whole-wheat bread making, which has special starter techniques to get the best flavor possible. I realize your question is about biscuits and not necessarily bread, and his book doesn't have anything to say about biscuits or quick breads.