This is the piece we just finished last week - beautiful computer/office cabinet of mahogany and wenge. I used Tried & True linseed oil - 5 coats on the top and 3 on the case.
But your artwork deserves a beautiful protection too - and here's one method that our friend Kathy recommends........
1) Apply seven coats of matte varnish. Do not sand between coats. Let each coat dry 20 minutes. After seven coats let dry overnight.
2) With 600 grit black wet-dry sandpaper dipped in one cup of water with one drop of dishing washing liquid (any brand) gently rub with the grain. Be careful to use a gentle touch, especially on edges or over dots. This dulls down any shine.
3) Wipe with a paper towel to dry.
4) Using #0000 steel wool pad and neutral Kiwi shoe polish (use a good amount) rub in hard.
5) Using a clean piece of #0000 steel wool wipe off excess shoe polish.
6) Buff with a clean soft cloth.
7) Admire and Enjoy!!
Stay tuned -- in the next few blogs I will give you tips on more finishes, sandpaper folding, and some smart working ideas from the wood shop... did you know that 'scotch brite' scrubbies come in different grits just like sandpaper??