Image Gallery with custom thumbs...?

Hello all,

I'm fairly new to RoR, have done many different tutorials, but am now
trying to build something on my own. I would like to create a
portfolio gallery. I plan on using customized thumbs, not scaled, but
custom cropped and resized in Photoshop. The reason for this is these
will not be photos but portfolio pieces and I would like the thumbs to
focus on a vital part of the piece. These will then link to the full
sized image (maybe a lightbox plugin or something).

Now I've been searching for how'to's and tutorials, but they all
mention using plugins such as "file_column" or "Attachment-fu" along
with an image processor (ImageMagick and such). Do I need to use these
tools to achieve my goal? Seeing as I will upload a full sized image
and a thumbnail image, I'm thinking I don't need the image processor
for this. But the plugins look like they will help with file storage
options. I would appreciate any input on this (code examples would be
fantastic. =P) .thanks!