De Bellis Renationionis or DBR (for the uninitiated) is a twelve year old set of rules from wargames research group (WRG), written by Phil Barker.   As a set of rules it never gained the popularity of the Ancients set (DBM), but has a small but devoted following.   The rules and the three sets of army lists enable battles to be fought from the French and Italian Wars of the 15th/16th Century, through the early colonial wars, and the upheavals and rebellions of the Seventeenth Century.

The picture above is of a couple of units from Paul's Parliamentarian Army.

There are a lot of resources out there on varoius websites, manufacturers, guides and some intelligent articles on both unifrms and flags.

https://www.baccus6mm.com/index.php?content=howto  

Baccus have painting guides on several periods.  This one take you to their ECW painting guides with some useful information on the Royalist Army of Oxford, and Essex's Parliamentarian Army.

http://www.quindia.com/studioart08.htm   I had not come across this site until i started researching online resources.  Some of the painting here  (25mm in this case) is truly inspirational.   Even better there are some free `downloadable' flags made available by the site owner.    

http://www.vexillia.ltd.uk/common/pdf/Uniforms30YW.pdf   The Vexillia site has an excellent article on unifrom colours for the Thiry Years War.

http://www.hz-forum.de/30_krieg_fahnen/alle_fahnen.htm    A German site with around 50 or so flags for the Thirty years war.  A few of these would be completey beyond me to paint, so another useful resource.     Cut and Paste!

http://www.angelfire.com/ak5/alexflags/tyw.html   More Thirty Years War flags

http://www.rofur-flags.de/listen6f/dreissigjaehriger-krieg-1618-1648-engl.htm  Even More Thirty Years War Flags!

OK that should be enough to get most people started!!