For my personal development I use an SVN and while it works great in my IDE I would also like to see things when I'm viewing my workspace in PCManFm. Are there any plugins that do this? I can't seem to find any in Google.
Since svn/git/etc. integration is not something that PCManFM intends to ever include, indeed such functionality would require a plugin. However, as the asker found, no such plugin appears to exist.
If possible, one can use a file manager for which svn/git/etc. support exists. RabbitVCS, which supports git and svn, has plugins for Nautilus (the GNOME file manager) and Thunar (the XFCE file manager).
(Thunar is probably the more one similar to PCManFM, since XFCE and LXDE are both lighter-weight desktop environments. Unfortunately, I have not found a good tutorial for making Thunar the default file manager instead of PCManFM when using LXDE.)