i want to add entrance signs for my rides but when i go to choose a billboard, there are no images available to use on it.

i have tried to fix this in the past but when i made an 'image' file for rct3, i was told there was already an image folder somewhere on my laptop and it deletes the new file

how can i fix this? signs make stuff look much better

Have a look at this tutorial "http://m.youtube.com/watch?v=txcNkpavGY8"
It also worked for me.

Sorry, I have it now I misunderstood the command. I have the same problem (no Billboards). I am running Windows 8.1. I tried the video but get an error with the rndir command. Any thoughts, I really would Like to have billboards again.

awesome, thanks. now i can cover up some ugly walls XD

Blu has the "RCT3 Billboard Fix" which will fix it for you.
Link: http://forums.rctgo.com/thread-6924.html
Yeah, it is very helpful.