Just like choosing a good wine ... it is all down to personal taste. If you like it then that is good enough - regardless of what others might think.
But how do you go about choosing the right painting to say what YOU want it to say. Different pictures make different assertions.
Here are some major statements:
1. Simply filling a wall space
2. Harmonizing your decor
3. Proclaiming your artistic prowess and astute eye for a good investment
4. Provocation
The first is in many ways the simplest to deal with. However, you do not want spaces filled with just anything so lets take a little time to consider the situation.
Choose a particular area - notice how the room relates to the space. The most common observation is of course that you are gazing at a number of straight lines - both horizontal and vertical. These in turn produce intertwining rectangles of varying sizes. Therefore the obvious choice would be to choose a work that is split up by straight lines, or includes rectangles. Once you are happy about the shapes you will be looking for then comes the colour. If you just want something decorative then a painting with similar colours to the surrounding area will tend to blend in, filling the space but not being too visible - a little like background music. If you are looking for something a bit stronger then look for bright or deep colours but of similar hue to the surrounding area. Having said that choosing a picture which has a lot of straight areas AND includes a splash of some other shape (say a broken circle or a gash of colour) will add a little extra dimension to the space to be filled. And if you want something even louder then you will have to wait until we talk about the provocation or challenge.
Harmonizing a room is a larger quest. Many people have succesfully harmonized their spaces using Feng Shui, and you will find many websites giving you specific tips. But you can make it far more personal by using your own observation and personal taste. To some the colour red means drama, alertness, and action, whilst others see green as relaxing, refreshing, light, and cool. What colours, then, would you regard as appropriate for your space? Put another way - what kind of space are you looking at? A quiet corner? A games area? The dinning room? ... Verbalize what the space is, then begin associating the space with the colour. For instance if I think of a dining area I am immediately taken back to my childhood ... dinner was served in a room of deep dark brown and light grey. I associate brown with food things like roasted food, chocolate, and that gravy my mother used to make - dark, delicious, and such a wonderful homely smell! Part of the beauty of harmonizing your space is that you can choose a number of paintings - all by the same artist. They will be different - and yet the same ... like an orchestra of different instruments all producing the same musical piece.
If you wish to be seen as an active knowledgeable art collector then you will have a lot of work to do. You will need to see what is the latest in abstract art - and make your own decisions as to whether you agree or if you dare to try to find your own choice of more innovative work. Do not just choose the well known artists - hunt out some of the more obscure painters. Find out as much as you can about them - get a "feel" for them and their work. You could end up being a trend setter, which will require you to make choices that many people will vehemently disagree with - but then again you might be the first to discover a true artistic genius. You are also at the cross roads between harmony and challenge. You can have one or the other ... or both! In this case the world is your oyster (that is if your budget will stretch that far).
The provocation is perhaps the most personal decision. Here your own history, your own personal life, your individual attitude to others and the whole world will be displayed - naked for all to see. Therefore it will be worth shouting about won't it!. Earlier we spoke about harmony - in this section disharmony, anarchy, aggression, and shock tactics are the rule of thumb. You will need to be precise in choosing your particular challenge. Once you have found it then seek out the painters who look towards the extreme of things - This is a dangerous yet exciting world where you may find yourself shocked. And just like the avid horror film buff, you may be looking for that image which will take you just a little bit further towards the edge ... and others WILL follow.