Yes, you can still probably install and use the BeOS, with some restrictions. The BeOS Release 4, available now, includes a "lowest common denominator" SuperVGA driver, which should work with most graphics cards.
This driver runs in 640 by 480 pixels in grayscale mode only. It is not terribly pretty or useful, and it is a performance hog, but it does let your system boot, and allows you to use the BeOS.
We do not recommend this driver for regular use. The design goal of the SuperVGA driver is to allow you to install and boot the BeOS, and use it long enough to download a real graphics driver for your card, from either the Be web site or your card maker's web site.