I'm not sure if you ever figured this out using only your ipod, but I recently spent about 10 minutes posting one picture on the forum from my flickr account all on my android phone, an ipod touch should work the same.
1. Go to flickr and find the photo you want. While using your ipod touch the UAstring should be set to mobile so the flickr site you will be at should be the mobile one. I'll use my most recent photo as an example, here is the link I see on my mobile device.
http://m.flickr.com/#/photos/bigcamphotography/5707608290/sizes/m/
2. Once you are at the picture you want, scroll to the bottom of the webpage and click the blue link that says flickr.com, this is underneath the copyright info.
3. This brings you to the same picture but at the normal www.flickr.com, here is the url I am at after clicking flickr.com
http://www.flickr.com/photos/bigcamphotography/5707608290/sizes/m/
Note: this still isn't the url you want.
4. From here I hold down on the picture and a few options come up, one is to view image. When I choose that it brings my picture up in a new window and the only thing displayed is the image. THIS is the url you want. I don't have an ipod touch, so I hope you have a similar option, here is the url I'm at now.
http://farm4.static.flickr.com/3588/5707608290_83525946bf.jpg
5. Once you have the correct url just add image tags to it and your set
[img=http://farm4.static.flickr.com/3588/5707608290_83525946bf.jpg]
Which yields us this
I hope this helps, it took me about 15 minutes to write up using my android phone, I only say that to remind you everything is slower when working on a small mobile device.