It may be difficult to equate terms such as 'Abstract' or any other form of 'art' to photography, because each specific 'school' - eg; Romanticism, Impressionism, Post-impressionism, Neo- impressionism, etc, etc, has undergone an evolutionary process with usually clearly identifiable features and leaders. Plucking out some of these features and characteristics and applying them to the art of photography, may not be appropriate, relevant , and definately not that easy.
Even within the confines of 'Abstract art', there are different styles, two of which - Abstract Expressionism and Cubism a more Geometric Abstract art. Regardless of the type of Abstract art, the common element was for the artist to represent his inner self - the non-visible - instead. The art which was created has no reference to any figurative reality. It is art that depicts real forms in a simplified or rather reduced way - keeping only an allusion of the original natural subject.
Kandinsky was one of the earliest 'Abstract artists'. His "inner necessity" to express his emotional perceptions led to the development of an abstract style of painting that was based on the non-representational properties of color and form.
Many Abstract artists explain - and it has become widely acknowleged - that the physical process of experimenting with and manipulating paint, charcoal, pastel, crayon or any other malleable medium, is inherently and an imperative part of the process of making 'abstract art'. It is this emotional ferver of the process, which is recognised as just as an important part of 'Abstract art' as the finished product.
If working in a 'state' where one there is an emotional drive to explore the physicality of the medium is one of the criteria and features of Abstract art, I am not sure whether this can be achieved at a computer - (making reference to digital processing here). Is it then valid to call an image 'abstract', even when it is clearly unidentifiable, yet does not satisfy one of the acknowleged criteria of the abstract form - that is - the emotional exploration of the physical medium in which the final product is made?
Perhaps this is the time for a new 'school' of art to evolve within the realm of Photographic Art, and create its' own jargon and characteristics, just as painters have done throughout history. With the development of the digital image, perhaps photography will develop more clearly, artistic styles other than documentary, landscape, portraits, fine art etc..., and not try to borrow or equate from previous art forms.
Perhaps in 20 years or so these new photographic styles with their own definate characteristics may have their own new label. For now, I see a difficulties in saying that something is abstract, just because it explores colour and form, and may be unidentifiable. Part of the process which makes Abstract art what it is, is missing, in the creation of a digital image. Of course..that may not matter... and until then there may not be a better term.