Gimpshop is just a little bit modified version of Gimp for Windows and Mac.
On Ubuntu, please just use the plain Gimp which is packaged fine in the main repositories and available straight form the Software Centre.
The package you downloaded appears to be a very blunt single package of Gimp 2.2 (really old!), built in 2006 (!) with all its dependencies in it. The README files reads
The GNU Image Manipulation Program Version 2.2
This is version 2.2 of The GIMP.
It looks harmless by looking at the content.
- It has no install script hooks (
postinst, etc.) in place. This means it's just a simple unpacking of files.
- The above makes it very clear: it's not responsible for removing the package from your download folder.
- The binaries themselves are hard to check. If you haven't run the program then you don't have to worry about it.
- The quality of the package is really poor and it appears to be built by a very simple "checkinstall" script. This may explain why Software Centre wasn't able to handle it properly.
So, just remove it completely using your package management:
sudo apt-get remove --purge gimpshop