Two great online sources for past trip reports:
www.portlandhikers.org (unfortunately their archives are unavailable, so trip reports cover only the past 2 summers).
Here is the official USFS website for the Wallowa-Whitman National Forest: http://www.fs.fed.us/r6/w-w/recreation/wilderness/ecwild.shtml
Barstad, Hiking Oregon's Eagle Cap WIlderness (describes all the individual trails but not much help in planning loops--once you've planned the loop, you can pick out the pertinent trail descriptions which are quite detailed)
Lorain, Backpacking Oregon
Lorain, 100 Classic Hikes in Oregon (some of the one-way hikes described in Backpacking Oregon are shown as loops here)
The GeoGraphics map of the Eagle Cap Wilderness is really crummy and hard to read. I don't know if the Forest Service has a better map, but if they do that would be the one to get to help plan loops.
The Lakes Basin is so beautiful that it's worth a visit. It has been suggested that you avoid it on a weekend, though. One less populated approach is from the south side, from the East Eagle trailhead. A loop is described in both Lorain books. I'm hoping to do this one next year.
The information you get from the Wallowa Mountains Visitor Center (phone on the USFS website) seems to be a bit lacking. I called in early September about the missing bridge on the East Fork Lostine River. All they told me was that the bridge is out and they hadn't maintained the very popular trail. I found out from several trip reports that there is a nice wide log across the river near the old bridge, and that just fording the stream at that time of year was no big deal (it might be in late July, especially if snowmelt is late). The folks at the Visitor Center didn't know anything about either of these options.
The Wallowas, being well inland, have a continental climate. Expect possible daily thunderstorms. As in the high Rockies (even though the Wallowas aren't as high), you can expect snow any month of the year, although probably least likely when you're going.