Since it was bugging me how I couldn't launch files from anywhere other than the root folder of SRB2, I decided to teach myself just enough of the Windows command line syntax to make a little batch script that fixed it. You're free to use it if you want:
start "" /d "%~dp0" /b "%~dp0srb2win.exe" -file %*
Basically just open up Notepad, paste that and save it as a *.bat file. Remember to pick "All Files" from the drop-down menu, otherwise it'll save as *.bat.txt, which isn't what we want.
Stick the file in the same folder as srb2win.exe. You can now launch any number of files at once simply by selecting them all and dropping them on the batch file.
To register a file association so you can just right/double-click on the wad file, just follow the steps in the guide, replacing srb2win.exe with whatever you named the batch file, taking care to omit the "-file" parameter as well. So you would have "C:\SRB2\loadfile.bat" "%1" or something alike.
Now, you ask, can you select a bunch of wad files, right click and open them all at once? I'm afraid not. I tried to come up with a solution for this, but I honestly think it transcends me. It's a part of how Windows handles file actions: it just calls the same program over and over. Which can't really be fixed because the -file parameter is only evaluated at start-up, so even if SRB2 were smart enough not to open up multiple clients, it still wouldn't be able to do a thing about the passed arguments.
I also went and fetched some
old icons to deck my folder with. These are the icons used for SRB2 itself, as well as the now defunct netgame launcher. Enjoy.
EDIT: Duh, I didn't notice the first icon was back in 2.0. I thought it still used the ugly broken icon (which srb2update uses) introduced some time during the 1.09 period. I guess you don't need it, then.
EDIT EDIT: Actually, it's different... it's bigger, but it's probably just upscaled... whatever.