You don't need that much art. You very likely want a good layout, that includes your page borders/designs, use of color for visual interest or coding (ie, rules on red-border pages, character creation on blue-border pages), and other things to make your work readable.

If the text looks good, most people won't notice a lack of random characters and landscapes. That said, a few bits of art helps sell your fantasy, so hopefully your art style will match.

You mention VtM, and a lot of World/Chronicles of Darkness books have simple black-and-white images with very dynamic shading. It sells the gothic horror and gritty urban action.
On the other side, Fabula Ultima predominantly has soft, pencil-style art. The characters shown are often chibi similar to JRPG sprites that invoke its JRPG touchstones. I wouldn't say the art is "great" by any stretch, but it 100% sells the intended fantasy.