A painting is a kind of picture. (given translation)
If I was told to translate the English sentence to Japanese I would have written 絵画は一種の絵だ, since the basic sentence is 絵画は絵だ not 絵画は一種だ.
If I were to translate 絵画は絵の一種だ to English I would say "a painting is of the picture variety"· This sentence sounds a bit more formal but essentially has the same meaning.
Are both Xの一種 and 一種のX grammatically correct? Do they have the same meaning? Do they have the same formality?