I don't know who this can help, but still

I have used several ways to tie a miniature to the base. 

First and most common is a weathering.  You use same color/pigment to weather base and lower part of miniature.  It's easy and work nice for most cases. For example my plague Marines, I use their grime and liquids to tie them to base.  Except you don't want dirty miniature or it's on flying stem. 

Second one is a miniature's  falling shadow on the base. It's link mini without weathering. It's looks good with bright vibrant color scheme. Also high contrast between miniature and dark shadow make your colors even brighter. It's nice for minis under sun or kind of direct light.  For example my recent IF KT. I use shadows there. But don't really work for darker environment. 

And for this case there is a bit more advanced technic. We can use reflected light. It's could be reflections on metallic surface. We can use metallic of same hue as our base, it can be color tint on armor or clothing of basing color. 

It's can be achieved with glazes or thined washes, inks also good solution. Obviously with NMM and volumetrics you could make it even greater.

Here is an example, with red and brown  reflections on armor and and tint on boots the viewer are sure guy stand on this roof. 

Hope it's helps someone to improve.

As always would be glad for any C&C.