I am looking to buy a digital camera to primarily take photos of my artwork that deals mainly with acrylic paintings. A previous question has helped me determine that a digital camera is the way to go. Is there any specific brand that is the best or I should keep in mind to stay away from? What specifications should I look for and are important in a camera for this use case?
Not really I'd say. You need a camera with a decent macro lens. But I assume and interchangeable-lens camera system includes a decent macro (personally I really like the Nikon 105mm, but there are many other manufacturers who are no doubt good enough [and the 105 may be too long for your use case])
More important will be the tripod you use, the arrangement you use for holding the artwork, and the illumination. The answers to your previous question provide some good pointers for those, I think.
The macro lens is important not for high magnification but because they usually have a very flat plane of focus. Since your artwork is also flat, this is important for getting all of it properly in focus. Most tilt/shift lenses also have very good flatness of field (better than macro lenses, often) but they also include features you will likely not need, and are therefore more expensive.
I'm not sure what you would propose to do with the digital mages. If you plan to print them very large (say more than 60cm on a side) then resolution may be an issue; otherwise not.
It is vital to know what you want the image for.
If you are making prints from the image there is a limited upper size that you can achieve at fine art quality.
In this questionWhich image sensor format for photographing oil on panel? I demonstrated that at 38 x 28.5" print size (!) from an ~A3 original you are better off using an A3 sanner than any 35mm DSLRavailable (including the D800). That may not apply in your case, but you need to check.
Megapixel image needed = height x width x dpi^2 / 1,000,000
height = print size in inches.
width = print size = inches.
dpi = pixels per inch in output.
This assumes that printer aspect ratio = camera or scanner aspect ratio.
Example: 16 x 10" (= A3) x 200 dpi.
megapixel = 16 x 10 x 200^2 / 1000000 = 6.4 megapixel.
So printing at A3 and 200 dpi a 6 mp imager is OK.
Push that to 300 dpi = 14.4 mp.
If you want 600 dpi (and you actually don't) at A3 you need a 58mp imager
A D800 cutteth not the mustard - the more so if you have less than top class glass on it.
In reality a good 12 mp camera will work well enough in most cases.
Lots of light is essential if sensor sizes are small. I once did a large billboard photo starting with a 7 mp image - but that was extreme and really too low.