Weellllll,IMO I would use glass for the baffels. I would buy either 3/16" thick cause that is what the tank is made of or 1/4" cause it might be a lot eaiser to find. I would get the glass at the local glass shop. The pannels of glass will be cheap. At least they are around here. Also if you don't have a table saw, then acuiring acrylic and cutting it your self will not help you any. Plus siliconing acrylic to glass is at best shakey. Lots of people do it but, not the best.
As for aquarium safe silicone with mold inhibitors.........No such thing. That silicone is NOT safe for any tank. You need to find GE type I window and door silicone. If not that, then get aquarium silicone by DAP or Aqueion ect.. The GE will be a few dollars cheaper then the "Aquarium" silicone.
I don't have any pics of my 20L sump as I am still building it and the design would not help you anyway. Sorry. As for what you want in there, The layout needs to be thought out real close before you go and buy anything. The stuff you didn't mention that most do use in thier fug is a skimmer, they also move thier heaters down there.
You mention micro algae and cheato. Micro algae and cheato (Macro) algae are two different beasts. The micro aka..(one type) Hair Algae will win out over the cheato as it is more efficent at using up nutrients. It must be one or the other and the only way I know of to utlize HA is to use a scrubber. This is yet another topic.
The LR and the sand, good stuff.
You also need to think about the return pump and where it will go. A internal or an exterinal pump.
I think that is all of your Q's for now. I hope this helps. Good luck.
Peace.
