use of thumbnail files

[HLFadmin]

Our forum displays the uploaded graphics, not thumbnails.
Our hosting is on a shared server, and our provider has an AUP with inode limits, even though file size is unlimited.
I want to know if I can delete the thumbnails and keep the full size files without impacting the forum display.
We have a 260K inode limit, and we're approaching 88%.

What are my options? 
Thanks in advance for suggestions.

[HLFadmin]

With 66 views and no answers, I'll have to try to answer my own question, although there is no certainty it is fully correct.

I created a mirror of the forum on a local server, then deleted all *_thumb.* files.
I am still able to see the posts with images as before.

However, I'm aware the mybb_attachments table has a populated thumbnail field.

So, I'll repeat my question. Is anyone aware of an impact to forum performance if the thumbnail files are deleted?