Thanks very much for all the nice comments and the +rep
As a question, are all of your bases custom built or have you purchased any and if so, from where? It has made my own attempts at basing seem quite paltry haha.
I make my own bases. I only have a small collection of items that I use, but I try new things out every now and then. I'll give a quick run down of some of the items I use
sand - this is a mixture of gw sand, display sand from ikea and very small pieces of slate.
PVA glue - for sticking down the sand
superglue - for sticking down grass and flock
plastic glue - for sticking down girders 'n shizz
plastic tubing - get this from a hobby store, you are looking for a few different sizes
plastic girders - again, from a hobby store
Gw basing kit - different sizes of slate and the brass etched stuff
car body mesh - from somewhere like halfords
various types of static grass and flock - from any hobby store
city of death components - don't use all the parts when building your Cities of death buildings.
I think that pretty much covers it.
When you are building your bases try and think of what sort of look you are going for and don't overdo it. If you are building a 10 man squad you don't want to have 10 massively unique bases as it will be too much. In many of my squads I only have 1 or 2 highly detailed bases, this draws the eye, just think of the rest of the squad as a frame for those members. These same rules really apply when you are building your models.
I hope this has helped.