Here are the options that I know of to blank them.
I use the foreign versions of each title card and I copy that part to the English title card, because they usually have very little text. I usually get them from YouTube, or from here
spongebob.wikia.com/wiki/List_of_episodes_(foreign)/languages
and here
spongebob.wikia.com/wiki/List_of_episodes_(foreign)/languages/Welsh
You have to copy and paste the links though.
You can also the watch the forgien episodes online.
You can get backgrounds from the show itself, like the Underwater Sun sequence from Party Pooper Pants.
You can get them from the theme song, because there is alot there :P
You can get them from the SuperSponge Assets Disc, where a lot of production art is found. (You can download it from here)
https://mega.nz/#F!xYNmwTaB!kW4Squ8sgqe96LZAcddGeQ!kA0kgaKb
You can also draw over it as fskw822 AKA NauticalSponge said as well. :)
You can find other title cards or time cards with the exact same background, like Wormy and Sandy's Rocket, whether it be forgien or English, it'll work. Make sure you adjust the colors if they have a different color pallete though to make it all fit though. Wormy has a slightly darker title card BG than Sandy's Rocket.
I hope fskw822 and I helped you a bit more