I add my 2 cents:
You can use some translucent white paper and cover the lamps with this to diffuse the light. This should avoid stark shadows.
That said, I would not go all in an remove all shadows. This is often a result of using a light box and I feel it removes any "life" from the miniatures if you go for a scenic shot. To simply show off your paint job the light box may be still best, as nothing will distract or alter your miniature.
I still like slightly diffused daylight best for photos. If you have a large window you could try taking pictures close to it, reflecting some of the light back onto the scene with a piece of white foamboard to avoid stark shadows on the side facing away from the window. That said, sometimes it is exactly what you want to achieve a certain atmosphere (for instance a dark forest).
I wrote a two-part tutorial on scenic miniature photography, have a look if you like. I obviously still take pictures with a neutral background and use the scenic ones for atmosphere or featured blog pictures.
https://daggerandbrush.wordpress.com/2015/04/19/shutterbug-how-to-take-scenic-photographs-of-miniatures-part-i/