Hi Mick and welcome to the forum,
Step 1, I would suggest learning all about the liquidation market before even starting to research actual liquidators. It's not a regular wholesale type market, you're dealing with a whole different animal when it comes to surplus. Most people get burnt because they really don't have an understanding of what they are buying in general terms.
So step 1 for me, learn the market you are wanting to deal in from a seller's perspective.
It's a waste of time asking for pics, because even if a supplier did send you a pic it would only be to give you a general idea of what the load would look like, you wouldn't get an actual pic of the load you were buying. The best thing to ask for is a manifest, this outlines what the load contains.
Now what will usually happen with a surplus lot is the supplier will make that lot up out of many different conditions. For example, 10% new shelf pulled stock, 70% customer returns and maybe 20% of damaged stock. That's just an example and not every lot is the same, but what the supplier will usually try to do is to average the load out so most lots have the same or close to the same ratios.
Now it's hard to make sense of a lot like that without understanding the market, for example, Shelf Pulls. This type of stock can include perfectly good new products that were just slow moving stock that was taking up shelf space, so it had to be liquidated. However, it can in some cases also include stock that was damaged on the shelf and was not then able to be sold, so this can end up in the same Shelf Pull stock pile.
So it's really important to work with a supplier who is open in regards to the makeup of a particular lot, but even then, you have to factor in a certain loss per lot. That's tales time to do because you need to run through quite a few lots to then be able to average out your loss rate.
This is one of the reasons that I say liquidation should never be looked at as a short term money maker. Most make money from it long term, but that's because they have spent the time assessing the lots and know within a certain percentage of how things will usually pan out on a per lot basis.
It really comes down to what you are buying, you can get lots like a Master Case lot. These lots are premium new products, no damage whatsoever, but naturally are usually more expensive because of the condition. Prices of lots are usually based on the stock type and condition makeup of the lot.
Doing things like buying a sample (if they allow it) might work if you are buying a lot full of the same item, but you still need to ensure that or just basing your purchasing decision on a single item may well bring you undone very quickly. Same for buying small lots, it's all about knowing what you are actually buying, not the size of the lot itself.
So big or small lot, one item of 2000 items, with liquidation it comes down to condition ratios of the lot you are buying.
One tip, never consider anything is worthless, you can be shocked at what can sell. Knife block without any knives still has value. A broken vacuum cleaner can be stripped and sold as parts and so on. When you deal in this type of market, you need to see value in everything, that's where people succeed in this market, on the little things that other's over look and discard.