My puppy has an upset stomach, and my vet told me to put him on a plain diet. So far all i've been giving him is chicken and rice, but I'm worried that as he is already fussy, turning down most shop brought foods, he might only eat chicken and rice in the future as he likes it so much. What other foods can I give him that are "plain" and wont upset his stomach any more? I would quite like to include some other things, like pasta or other meats maybe?? I'm not really sure what is considered "plain" as this is my first dog.

The plain diet is usually only advised as a temporary measure until the dog's upset is cured, when you start gradually re-introducing his normal diet. Did your vet specify that this was to be a long- or short-term measure?

Edit: How old is he? I've just noticed you said he 'turns down most shop-bought foods'. A pup needs any changes in his diet to be introduced gradually (taking at least a week for each changeover), especially if he's very young, or the dietary change in itself can cause diarrhoea.

Chicken and rice is not asufficient diet to raise a pup on.As JG says it is supposed to be a short term aid in clearing the upset tummy...the dog then needs to be gradually reintroduced to a proper diet
Archer

I find fish or tripe a plain alternative. Only adding one at a time of course. Anything new needs to be added slowly only replacing a small amount to the usual chicken and rice and increasing as you find the poops ok.