Hi, right now I am forming a psychedelic blues band with some of my friends, and so far we have a frontwoman, a bassist, an organist, a drummer, and myself on guitar. The thing is, I've had limited experience as the sole guitarist of a band and I'm not quite sure how I should strengthen my playing without a rhythm guitarist. If anyone has any tips about this, please tell me, any help would be greatly appreciated. Bye.
The really important thing is to be aware of what sonic space everything is taking up and what you need to do to fill out the sound, or even if you need to take up more sonic space.

Basically what we're talking about here is register, the bass and potentially organist will fill out the low end, lots of what the drums are doing will fill up the high-end and the front woman will be out front and basically in the mid-range (I assume anyway).

So you need to think about what space you need to be taking up at any point; if you need to fill out the sound more then it's going to be bigger chords, more tones even if not more notes. If the organ and bass are taking up a lot of space then maybe drop back to something simple and single-note based.

It takes a bit of learning to really get it but that's the basic idea, it's being aware of what everyone else is doing, what the music needs, and how to achieve it.
R.I.P. My Signature. Lost to us in the great Signature Massacre of 2014.

Quote by Master Foo
“A man who mistakes secrets for knowledge is like a man who, seeking light, hugs a candle so closely that he smothers it and burns his hand.”

you can treat the organist in alot of cases as a "rhythm guitar" giving you harmony as the bass is usually going to be doing the low end the organist has the choice of takign up lower registers and playng harmony and even melodies(if the organist is real good can do all three at the same time)
the singer is going to be round the upper midrange which is where guitar is usually at so you need to decide what to do in fact you have alot more options having a key player in the band you just need to work on not making your sound too muddy id definately keep the bass knob on your amp in the lower area

now about part writing just take it song at a time and dont write or play like if you were a sole guitarist you have othe rinstruments that can and probably would be in your sonic area
Well that is the position I play in the current band and I like it a lot. I play almost entirely covers and don't really approach it through the lenses of the posters above me. I figure the bass and drums are the meat and potatoes, keys is the salad, and guitar is the pepper and BBQ sauce. We make everything taste better. When playing rhythm, lock into the groove with the drummer and bounce off the snare and hi hat. When soloing, be bold and really let the dogs out. These other guys are laying it down for you so give em the pepper and take em on a ride.

Listen to other psychedelic guitarists to get ideas. Robbie Krieger is a personal favorite.
"Your sound is in your hands as much as anything. It's the way you pick, and the way you hold the guitar, more than it is the amp or the guitar you use." -- Stevie Ray Vaughan

"Anybody can play. The note is only 20 percent. The attitude of the motherfucker who plays it is 80 percent." -- Miles Davis

Guthrie on tone: https://www.youtube.com/watch?v=zmohdG9lLqY
"rhythm" is a role in the band, not just an instrument. Keyboards, strings, horns, 2nd guitar, chorus... all "rhythm". Try listening to bands that have busy rhythm sections to hear how the guitars find their space.

Steely Dan tunes are great for subtle and effective use of space when it comes to guitar. Old Funkadelic or James Brown stuff, too. Really, listen to any band with a horn section and you'll get a lesson in how to play "small" guitar parts.
You can check out some bands with single guitarists. Say Black Keys, Extreme, Stevie Ray Vaughan, Cream, Bon Jovi, Richie Kotzen. Depending on what you play, you could either do mainly rhythm guitar or do both lead and rhythm. I believe Eric Clapton is pretty good and doing both lead and rhythm at the same time, so you can check out his live playing.