Looks good! I've used coins for 15mm & 20mm figures and a friend of mine uses 2p coins for 28s but I like the look of the 30mm lipped bases. When you fill in the recess it really hides the figure's own metal base without it looking like it is stood on a mound. I also bought some resin "lipped" bases with a cobbled surface. The problem I was then faced with was snipping off all those metal bases that your figure is currently stood on, then I had to drill and pin the figures' heels (this included all gun crews as well). Very tedious, so think your project through before embarking on it!
I use 1p coins and build up the base with coarse sand and various bits of detail; I don't notice the little mound, but some might. I've used 2p coins two-man teams and people lying down and thought about them for single figs (to give me extra room to playa round with basing details), but I decided it it might be a little too big if I wanted to fit them into trenches, buildings, behind walls etc.. The lipped base get rid of the mound, but of course you then have the deep sides of the base, which personally I don't like, but others don't mind.
"You're a big man, but you're in bad shape. With me, it's a full time job." – Lt. Bromhead to Prince Dabulamanzi before the Battle of Rorke's Drift.
Think I'm going to go for the 2p base, because I quite like having a rather wide base after always having those small GW ones for LotR mini's. I just need to make sure I remember to have the trenches wide enough when I make them.