Hi there. Welcome to Dakka.
First off, nice scenery

It needs a more battered look applying to it maybe, but that's for the Painting and Modelling thread you're about to create for them.
Drop into the P&M section of Dakka's forums, and make a thread to showcase your stuff.
You have already tagged the gallery pictures, so that'll help.
Get a signature entry in your profile here, directing people to your gallery section. Ask for Comment and Criticism, and grab a link from the Gallery area to show them where to look. We're a lazy old lot, and linkies go a long way.
For Facebook, there are lots of groups for stuff like you mention. Start by joining a general
40k group, and look for posts from people talking about scenery and such. Follow their links and join them, too.
Otherwise, post up more. We wanna see your stuff.