As discussed in the last post, the idea behind PhyloPic is to provide "silhouette images of organisms", in other words just the black outline of the organism. That works well if you want to illustrate a phylogeny of insects, dinosaurs or mammals, because these taxa have very distinctive overall body shapes. It does not work quite as well if you want to illustrate a phylogeny of flowering plants, unicellular algae, or worms, for example.
There are two distinct problems. The first is that the truly relevant differences between organisms may be in their individual organs like flowers, leaf shapes, fruits, or mouth parts, for example, as opposed to the whole body. So to be useful, a collection of silhouettes should include individual parts of the organisms in question.
Second, a silhouette of an intricate organ like, say, a flower, may miss all relevant structure. Take this one, for example. When I first saw it as a small icon, I vaguely thought it might be a marchantoid liverwort, or maybe a particularly complex plankton species. It would not have occurred to me that it is a Hibbertia flower until I looked at the taxon name it was associated with. No, in a case like this it would really be good to see stamens and style, or to have gaps between petals and sepals.
Consequently, to maximise the utility of such an image collection across diverse groups of organisms, one would hope the definition of silhouette could be relaxed to include artwork with a bit more structure.
And apparently the PhyloPic collection is already somewhat flexible. In addition to silhouettes in the stricter sense, there are at least two other types of images in the database, although admittedly they are rare: Silhouettes that employ black and grey elements as in these recently submitted insects, and black silhouettes that also allow for white elements to visualise structural complexity as here.
For purely aesthetic reasons, I would prefer the latter. Obviously they also require some thought and talent. They would have to avoid lines that are too thin so that they still look good when scaled down. But the mayor challenge is simply to capture, using only black and white areas or perhaps only black areas with white gaps between them, the characteristics of a flower or fruit so well that (a) people will recognise the organism, (b) everything is morphologically correct, and (c) the result is attractive.
Scientifically correct botanical clip art could actually be something like a very special art form - just like of course new forms of visualisation, each with unique constraints, have always inspired botanical art.