Is adorning statuary a common worship/ritual practice in Hinduism?
Yes, it is among the offerings during pûja ! But it's more a temple practice, some Hindus do it at home too, in their home shrines... It can vary from an offering of unbroken rice (akshata, instead of clothing) or a simple piece of cloth or a entire, elaborate dress.
It's a more common and elaborate practice in Vaishnav sects.
What more can you tell me about it?
I find it's a beautiful practice, it's a show of reverence and love, and also it makes the murti kind of more "alive".
Are chosen adornments deliberately symbolic, or more like a personal aesthetic?
Traditionally, some ornaments and clothes have symbolism attached to them. For exemple, there is a very strict set of rules for dressing Radha-Krishna deities, like the head covering, feather on turban, the direction of the flute and what Radha should hold in Her right hand, what jewellery to use at what time of the day etc... But this is more for ISKON actually. Usually female goddesses wear saree, there is symbolism with the color of the clothes for each godesses or time of the year... Lingam can also be dressed too, with white or saffron clothe tied to it's base...
These are all mainly practiced in temples. At home, people do it very simply usually and don't really bother so much rules.
What positive elements does the practice add to your devotions?
Focus, peace and devotion.
What are some other books or resources I can consult to study it a bit on my own instead of pestering you guys with a billion questions about it?
I'm not bothered at all personally XD
I don't have any book or anything that explain it in details... Soooorrrryyy ! Do you forgive me if I post beautiful pics instead ?
On a side note, there are other eastern religions (oddly, mostly folk or popular/local mysticism and paganism) where clothing God(s), Godess(es) or holy objects, places etc is common. For exemple, Shenism and Thai Buddhism: