This is a classic layout. I have often seen the shower moved against that back wall, incorporating the window (which is changed to glass block). The toilet would probably move to the spot the sink is currently in (depending on how your floor boards run), with the sink across from the toilet. But that finished basement makes it a little tricky, and every time you move plumbing you are adding $$$.

So I'd take a different approach. Keep the shower where it is, and add a glass show door -- it will add a huge amount of space visually. Consider putting either 12" deep or 18" deep cabinets, rather than the standard 21" deep vanity, and put in either a vessel sink or a thin trough sink. Run those thin cabinets to the wall, incorporating the space where your trash can is now. You could also consider an 18" depth for the sink area, diving back to a 12" depth that then runs to the wall. You can also look at having the faucet for the sink be wall mounted over the sink, rather than taking up counter space. It is a little extra in plumbing cost to move the water lines up the wall, but worth it.

Also look at toilets, some are not as deep or long as others, which might give you more clearance between the toilet and the shower.

Now this is going to seem silly -- but ditch the blinds. If you need privacy, consider frosted glass. I know that seem ridiculous, but in a small space, anything that removes the visual clutter with help. And getting more light from that window will really help.

Good luck!