Hello student ,

Yes , you can do IAS after interior designing but note that if you have done diploma in interior designing then it is considered equivalent to intermediate only. Diploma is not considered equivalent to degree and for  the examinations of UPSC , you are required to possess any bachelor degree irrespective of nature & mode of the degree. You must have obtained the bachelor degree from an UGC approved university.If you seriously planning to go for Civil Service examination, then first of all, you have to go for completion of graduation degree in any discipline.

Hope it helps !