Is it okay if I bake a cake and make icing from scratch and not use vanilla?!
Answers:
Not really if you have a different flavor ( orange,almond or whatever) it will just give a little different taste. Or dont use any it just wont taste as good, it will still be allright.
If it is a chocolate cake and icing you won't notice much difference. If it is a yellow or white cake it will be noticed a little. If you have almond extract use a half a teaspoon for the teaspoon of vanilla.
In the icing you can substitute with the almond. If the cake you are making is a spice cake it wouldn't be missed. You could add cinnamon to your icing for flavor for that.
Yes, it'll be a bit flat and too sweet. Do you have any almond or lemon extract? You could add a dash of rum or a flavored liqueur like gran marnier, framboise, kahlua, or other flavor, rather than just have it flat.