There are of course two obvious ways to do this:
1 Hand-paint them;
2 Take your money to the nice man at Little Big Men Studios.
Now I'm willing to have a go at number 1. I mean, I hand painted the flags for my Anglo-Saxon and ECW projects! But having tried it I have struggled to get a nice, clean design on the small (9mm) Pictish cavalry shields. So, on to the second option.
There are two issues with using LBMS for this application. The first, and perhaps the most obvious, is that their range doesn't include any 28mm Pictish shield decals suitable for this size. I looked around at the various 15mm designs, but none were quite right, and Steve Hales at LBMS were kind enough to inform me before I handed over my money that the quite deeply convex shape of the shields I have might not work terribly well with their decals. I thought this was very decent of him!
Which left a dilemma. So, after due consideration, I made my own.
My experience of using various image manipulating software to make banners etc has been variable. Some have worked quite well, others far less so. Some of it might be the limitations of my entry-level Kodak inkjet, and some the limitations of the bloke using it, but some, I discovered, was more fundamental.
I had been cheerfully using PhotoShop to cut, paste, shrink and recolour images. The problem with this is that PhotoShop (and others!) use bitmap based formats. And as you shrink or expand images, the bitmap definition disappears... Armed with this information, I downloaded a copy of Inkscape (it's free), which is a vector-based graphics package, and started playing with it. I'll put my hands up and say that I found it quite difficult, but then, other than some time doing digital microscopy, I've spent my working life NOT doing image manipulation!
The big deal is, using Inkscape you can import bitmap images, and convert them to vector graphics that are (essentially) immune to losses in definition from re-scaling. Using my own hand-drawn images I scanned plus free content from the web, and background shield disks created in PhotoShop using the airbrush function, I made up a series of designs. Along with some inkjet decal paper, courtesy of Ebay, I was in business. Just remember one thing: inkjets don't (generally) print white - they use the background colour of the (white) paper! So, if you want a white, or off-white design, go with white decal paper.
So, via the magic of Inkscape, you can get from these:
The offending items - actual decals!
And here, again, in situ.
Pictish cavalry, with decorated shields
Personally I wouldn't describe it as easy, but to someone move savvy with image manipulation (i.e. most people!), it's probably a doddle. I managed to ruin one decal applying it, so had to scrape it off, print a fresh one and start again. On shields as curved as this, in days of old I would have gone with the MicroSet / MicroSol approach as used on model aircraft. However, I'm not sure that it wouldn't simply eat my decals if I did! A little trimming with a scalpel saved the day, though.
Even in close-up, I think they look OK. See what you think.
If you can read my shield, you are much too close...